A revision of descurainia Webb & Berth. Section sisymbriodendron (christ) O. E. Schulz in the Canary Islands

              BOTÁNICA MACARONESICA 4 (1977)
A REVISIÓN OF DESCURAINIA WEBB & BERTH. SECTION SISYM-BRIODENDRON
(CHRIST) O.E. SCHULZ IN THE CANARY ISLANDS.
DAVID BRAMWELL
Jardín Botánico Canario "Viera y Clavija" del Excmo. Cabildo Insular de Gran Canaria
RESUMEN
La sección Sisymbriodendron del género Descurainia {Cruciferae-Sisymbrieae) es en­démica
de las islas Canarias. En esta reyisión se estima que contiene 7 especies en su ma­yoría
de distribución local limitada. La morfología, citología y sistemas de reproducción del
grupo se consideran y las llaves y descripciones para la identificación de las especies
presentadas.
SUMMARY
The section Sisymbriodendron oí the genus Descurainia (Cruciferae-Sisymbrieae) is
endemic to tihe Canary Islands. In this revisión it is considered to conitain 7 species mo&tly
of limited local distribution. The morphology, cytology and breeding systems of the group
are considered and keys and descrrptions for identification of the species presented.
CONTENTS
Introduction 31
Material & Methods 32
General morphology 35
Cytology and breeding systems 39
Systematic treatment 42
References 53
INTRODUCTION
The genus Descurainia Webb & Berth. Cruciferae (Sisym-brieae)
occurs through North and South America, Eurasia, the Me-diterranean
región and Macaronesia. It is closely allied to Sisym-hrium
and Lycocarpus but differs from them by the distinct median
vein in the siliqua valves and subcapitate stigma.
31
DAVID BRAMWELL
Descurainia with about 50 species has three main centres of
diversity, to the South and East of the Great Basin of North
America, the Andean highlands, and the Canary Islands in Maca-ronesia.
The members of the genus found outside the Macaronesian
región are all annual or biennial herbs of Section Descurainia
(Sects. Sophia Webb & Berth and Seriphium O.E. Schulz) but the
Canary Island endemics are all perennial shrubs of the section Si-symbriodendron
(Cbrist) O.E. Sehulz.
The first description of a species of sect. Sisymhriodendron
to appear in the literature was published by N.J. von Jacquin in
1787 under the ñame Sinapis millefolia Jacq. Aitón (1789) transfe-red
this species to Sisymhrium and in 1836 Webb & Bethelot esta-blished
the sepárate genus Descurainia with D. millefolia (Jacq.)
Webb & Berth., D. sophia (L.) Webb & Berth. and D. irio (L.) Webb
6 Berth. D. irio is, however, generally considered to be a true Si-symhriuvi
species.
In 1888 Christ returned D. millefolia to Sisymhrium in
which he established the section Sisymhriodendron and added two
further species S. preauxianum Webb and S. hourgaeanum Webb
ex Christ to it. In his revisión of the tribe Sisymhrieae in 1924 O.E.
Schulz reestablished the genus Descurainia and transfered Christ's
section Sisymhriodendron to it. Since Christ's original publication
of the section new species have been added to it by Pitard & Proust
(1908), Sventenius (1953) and Bramwell (1973) giving a total of
7 Cañarían endemic species.
MATERIAL & METHODS
This revisión was based on herbarium speimens from the
following herbaria: British Museum (Natural History) (BM), Ro-yal
Botanic Gardens, Kew (K), University of Reading (RNG), Her­barium
Universitatis Florentinae (FI), Jardin de Aclimación de La
Orotava (TEÑE), Jardín Botánico Viera y Clavijo (JVC) and on
living material of known wild origin from the following: Univer­sity
of Reading Botanical Garden, University of Oslo Botánica] Gar-den,
I.N.I.A. Madrid, Jardín Botánico Viera y Clavijo as well as
ampie field studies.
Cytological data were obtained from material of known pro-venance
grown at the University of Reading and at the Jardin Bo­tánico
Viera y Clavijo or from seeds and buds coUected in the field.
32
REVISIÓN OF DESCURAINIA IN THE CANARIES
Figure 1. Leaf and leaf-isagment variation in species of Descurainia sect. Sisymbriodendron.
lA. a-c D. artemisoides, d-gD. gonzalezü, h-n D.lemsu (h=prímaiiy segment),
o-p D. bourgaeana, q-s D. preauxiana.
33
DAVID BRAMWELL
IB. a-j D. millefoiia.
34
REVISIÓN OF DESCURAINIA IN THE CANARIES
The author would like to acknowledge the considerable as-sistance
given in the carly stages of this revisión by B. Petty MSc.
at the Dept. of Botany, University of Reading.
GENERAL MORPHOLOGY
Habit. There are two basic chamaephytic growth-forms within
the section, a) a candelabra-shrub type with a well-developed cen­tral
axis and short branches. D. artemisoides Svent., D. lemsii Bram-well
and D. gilva Svent. have this growth-form and the very varia­ble
D. millefolia may be of this type or b), a compact, rounded
habit branching freely from the base and without a definite cen­tral
axis (D. hourgaeana (Webb ex Christ) O.E. Schulz, D. gonza-lezii
Svent., D. preauxiana (Webb) O.E. Schulz).
Indumentum. All species have both branched-substellate and
unbranched hairs as well as glandular triphomes. The types of hair
present may prove to be a useful character in infrageneric classi-fication
but this requires further study. The distribution and den-sity
of the indumentum is important for species delimitation in
some cases within the section Sisymhriodendron. D. preauxiana has
very few branched hairs and the indumentum consists mainly of
glandular trichomes. In D. lemsii, however, glandular hairs are al-most
completely absent. The density of indumentum in D. lemsii
and D. hourgaeana varíes considerably in cultivation but the pro-portions
of each type of hair remain relatively constant.
Leaf-shape. Though variable within species the degree
of división of the leaves is a character of considerable taxonomic va­lué
within the group and a range of leaf-shapes is shown in Figu­re
1.
D. hourgaeana, D. millefolia, D. lem.sii, D. artemisoides and
D. gilva have 2- to 3-pinnatisect leaves with lobes of varying width
whereas D. gonzalezii and D. preauxiana have pinnate leaves with
linear lobes.
Petáis. There are two basic petal-shapes within the sec­tion
(Figure 2) oval and cunéate into a distinct claw (D. millefolia,
D. artemisoides, D. lemsii, D. gonzalezii, D. gilva) and ovate to
oblong-ovate, narrowing gradually into a short claw (D. hourgaea­na,
D. preauxiana). The length of the petal, the shape of the limb
and the ratio of limb-to claw-length are generally reliable charac-ters
except in D. millefolia where the petal length is quite variable.
This species sometimes has slightly lobed petáis.
35
DAVID BRAMWELL
Figure 2. Petal shaipes in Descurainia
A-B D. artemisoides, C. gonzalezü, D-F D. millefolia, G. D. tourgaeana, H,
D. preauxiana, I D. lemsii.
36
REVISIÓN OF DESCURAINIA, IN THE CANARIES
Figure 3. Fruiting Inflorescences in Descurainia
A. D. gonzalezii, B. D. lemsii, C. D. preauxiana, D. D. bourgaeana, A. D. mi-llejolia.
37
DAVID BRAMWELL
Fruits and seeds. The angle between the inflorescence
axis and the base of the pedicel and the consequent orientation of
the siliqua (patent, erect or ascending) is a reliable character for
the separation of species in the group (Figure 4). The size of sili-quae
and the number of seeds per valve is also useful in several spe­cies.
Several species have siliquae in which the seeds are biseriate
rather than the normal uniseriate (Schulz, 1924). Detling (1939)
has shown this variation to be associated with the width of the sili­qua
and the size of the seeds and certainly in D. millefolia and D. ar-temisoides
the wider siliquae tend to have two rows of significantly
smaller seeds whereas the narrow fruits have a single row of lar-ger
ones. Seed-Shape, size and colour are, however, of valué as ta-xonomic
characters within the group.
CYTOLOGY AND BREEDING SYSTEMS
Chromosome Numhers. The chromosomes of Descurainia are
uniformly small and form a polyploid series based on X=7 (Bald-win
& Campbell, 1940). Most of the Central and South American
species are diploid with the exeption of D. myriophylla (Willd.)
R.E. Fríes which is locally tetraploid (Mantón, 1932). The North
American species form a polyploid series up to hexaploid (2n=14,
28 and 42). The Eurasian/Mediterranean D. sophia is tetraploid
^<V (¿/(V
r4^
0^
Figure 5. Mitotic Ohromosomes of Cañarían Descurainia species, A. D. lemsii, B. D.
preauxiana, C. D. bourgaeana, D. D. artemisoides, E. D. millefolia
38
REVISIÓN OF DESCURAINIA IN THE CANARIES
SPECIES 2n n AUTHOR,
D. artemisoides 14 Borgen, 1969
Bramwell, unpubl.
D. bourgaeana 14 Larsen, 1960, Bramwell,
Bramwell, unpubl.
Borgen, 1969
D. gonzalezii 21 7
14
Bramwell, unpubl.
D. lemsii 14
D. millefolia 14 Larsen, 1960
Bramwell, unpubl.
D. preauxiana 14 Borgen, 1969
Bramwell, unpubl.
Figure 4. Chromosome numbers in Cañarían Descurainia species
39
DAVID BRAMWELL
(2=28) and all the Cañarían endemics of sect. Sisymbriodendron
are diploids (2n=14) with the possible exception of some indivi­duáis
of D. gonzalezii.
The chromosome numbers of the Cañarían species are shown
in Figure 4, D. gilva being the only uncounted species in the group.
D. gonzalezii, a rare species from the subalpine zone of Tenerife,
seems to have both diploid and tetraploids in two populations ana-lysed
at El Parador and Boca de Tauce (Figures 5 & 6). Borgen
(1969), however, also reports triploid plants in this species grown
from wild-origin seed. Borgen's material may well have come from
a hybrid between diploid and tetraploid individuáis and data on
the fertility of the progeny as well as further analysis of wild po­pulations
of this species would be of considerable interest.
B <^
mU
• • •
Figure 6. Meiolic ohromosomes of Oanarian Descurainia species, A. O. lemsii B. D. bour-gaeana,
D. D. gonzalezii n=14, D. D. gonzalezii n=7.
Breeding System. Compatibility tests were carried out on
the foUowing Cañarían and non-Canarian species.
Cañarían species
D. artemisoides
D. bourgaeana
D. gilva
D. lemsii
D. millefolia
D. preauxiana
Non-Canarian species
D. pinnata ssp. glabra
D. pinnata ssp. menziesii
D. sophia
Some plants were isolated by bagging inflorescences and
others by placing them in sepárate insect-proof greenhouses. Con­trol
plants were allowed to develop their inflorescences normally
amongst plants of the same species or were actively cross-pollinated
40
REVISIÓN OF DESCURAINIA IN THE CANARIES
1/1
o
.S
Cu
•".Sí
§ ^
e 53 s
o
Percentage Siliqua formation
1. D. artemisoides
2. D. bourgaeana
3. D. gilva
4. D. lemsii
5. D. preauxiana
6. D. millefolia
7. D. pinnata ssp glabra
8. D. pinnata ssp. menziesii
9. D. sophia
0
0
0
0
0
0
75
75
75
0
0
0
0
0
0
100
95
100
74
53
50
46
50
65
100
100
100
SI
SI
SI
SI
SI
SI
SC.
se.
SC.
Figure 7. Compatibility tests on species of Descurainia 1-6 shrubby peiemiials SI, 7-9 íier-baceous
annuals S/C.
41
DAVID BRAMWELL
from other individuáis of the same species. The number of siliquae
formad with viable seeds was compared with the number of po-tential
siliquae (number of individual flowers formed in each in-florescence)
and a percentage fertility calculated (Figure 7).
The results indícate that the perennial Cañarían species are
strongly self-incompatible whereas the annual or biennial non-Ca-narian
species are self-compatible. This would appear to be in ac-cordance
with the general trend from self-incompatibility to self-compatibility
shown in other genera with annual, herbaceous wee-dy
taxa derived from perennial frutescent ancestors.
This trend towards inbreeding is also found in floral mor-phology,
the outbreeding Cañarían shrubs have large, bright yellow
petáis and conspicuous nectaries but the herbaceous annual mem-bers
of section Descurainia have smaller, palé yellow or whitish
petáis and small nectaries. As Baker (1959) points out there is a
strong correlation between perennial species and self-incompatibi­lity
and annuals and self-compatibility and that the general trend
is for outbreeding to be replaced by inbreeding rather than the re­verse.
In the case of Descurainia the change in breeding system
coupled with cytological and morphological data seem to indícate
a relictual nature for the shrubby Cañarían taxa probably appro-aching
the ancestral state of the other sections of the genus in habit,
chromosome number, breeding system etc.
SYSTEMATIC TREATMENT
Descurainia Webb & Berth. sect. Sisymhriodendron (Christ)
O.E. Schulz. Shrubs, base very woody. Lower leaves with dense,
leafy axillary fascicles. Buds ovoid, not overtopping flowers. Flo­wers
large; petáis 3-6 mm, the lamina oblong to ovate, bright yellow,
narrowing into a claw. Ovary cylindrical, 2-4 mm long. Siliquae
more or less 4-angled; val ves keeled. Seeds often slightly winged
at apex and striate-granular. Canary Islands.
Type species D. millefolia (Jacq.) Webb & Berth.
KEY TO SPECIES
1. Sepáis less than 2.5 mm, petáis 3-4 mm.
2. Leaves more or less sessile, primary seg-ments
decurrent, pedicels of siliquae
patent D. bourgaeana
42
REVISIÓN OF DESCURAINIA IN THE CANARIES
2. Leaves shortly petiolate, primary seg-ments
not decurrent, pedicels of siliqua
ascending to erect D. gilva
1. Sepáis 3-4 mm, petáis 5-6 mm.
3. Lower leaves pinnate, lobes, linear, acute.
4. Plants branched at base, leaves canes-cent
with branched hairs D. gonzalezii
4. Plants branched above, leaves green,
with glandular trichomes only D. preauxiana
3. Lower leaves 2- to 3- pinnatisect, lobes
linear-lanceolate to ovate, obtuse to
acute.
5. Lower leaves petiolate, usually 3-pinna-tisect,
siliquae usually less than 20-see-ded
D. millefolia
5. Lower leaves subsessile, usually 2-pin-natisect,
siliquae 20- to 34- seeded.
6. liCaf-lobes elliptic-ovate to spathulate,
Siliquae about 20-seeded D. artemisoides
6. Leaf-lobos linear-lanceolate, Siliquae
28- to 32- seeded D. lemsii
1. D. gonzalezii Svent, Bol. Inst. Nac. Inv. Agron. 28:17 (1953) Si-symbrium
gonzalezi Svent. in exsicc. Fiera Selecta Canarien-sis
n° 218 (1950) nomen nudum.
Shrubby plant, 100-150 cm high, strongly branched at base,
very woody. Branches erect, terete, covered by withered leaves;
densely leaved but becoming sparse above; cortex of young bran­ches
creamish and of oíd, yellow to palé grey, splitting, covered in
white branched hairs up to and including sepáis, which have occasio-nal
long unbranched hairs. I^ower leaves slightly pinnate, upper lea-ves
entire, 2 - 5 cm long, palé nerved; segments 1 mm wide, linear,
acute. Inflorescence unbranched or sparingly branched; pedicels 8 -
10 mm long; sepáis 3 mm long x 1 mm wide, linear-lanceolate ob­tuse,
erecto-patent; petáis 5 mm long, lamina oblong. obtuse slightly
undulate, equalling claw; stamens 2.5 - 3.0 mm long. Pedicels and
siliquas lying cióse to axis of inflorescence; siliquas glabrous, linear,
erecto-arcuate, about 2 cm long and 1 mm wide, gradually attenuate
at both ends; septum 1 — nerved; seeds oblong-ovate, compressed,
reddish, uniseriate. Figure 8.
43
DAVID BRAMWELL
O
< >
Figure 8. Distribution of D.gonzalezU.
Type: In ínsula nivaria reg. alpina "Las Cañadas" prope ru-pes
"Azulejos" ad 2.200 m. supra mare. 28 aprilis 1944. E. R. Sven-tenuis
(TEÑE).
Other specimens: Canary Islands, Tenerife; Las Cañadas,
2.100 m. 30.4.1969, Bramwell 1414 (RNG); Las Cañadas 2.000 m.
26.7.1972, Bramwell 3518 (RNG); Filo Las Cañadas 12.6.1899 R.P.
Murray S.n. (BM), Las Cañadas, Montaña de las Arenas Negras,
20.5.1846, Bourgeau 682 (BM, K).
A rare species of the subalpine scrub vegetation of Las Ca­ñadas,
D. gonzalezii is found on lava and volcanic debris at about
200 m. Like D. hourgaeana which is found in the same área, this
species overwinters as a few short woody stems which produce
new shoots in spring after the winter snows have melted.
2. D. hourgaeana Webb ex O.E. Schulz, in Engler Pflanzenr. 105:
345.
Sisymhrium bourgaeanum Webb ex Fourn, Recherch. Crucif.
55 (1865)
D. bourgaeana Webb in Bourg., Pl.Can.Exsics. 1268 (1855)
Nomen nudum.
D. hourgaeana Webb ex Christ, Bot. Jahrh. 9:89 (1888) in
synon.
Branched shrub, woody at base, 25 - 65 cm high; young stems
erect, greyish, more or less glabrous above, densely leafy below; ma-ture
cortex wrinkled and split. Leaves in axillary fascicles 2-pinna-tisect,
ovate, sessile, up to 4 cm. long, green-grey, tomentose with
44
REVISIÓN OF DESCURAINIA IN THE CANARIES
branched hairs interspersed with glandular trichomes, primary seg-ments
decurrent, 3-toothed at a,pex; secondary segments shortly aeu-te.
Upper leaves petiolate, pinnate; segments linear-lanceolate, often
3-toothed. Inflorescences usually simple, erect, pedicels 6-10 mm
long, sparsely pubescent with branched and glandular hairs. Sepáis
2.0-2.5 mm with branched glandular and occasionally long, unbran-ched
hairs. Petáis 3-4 x 1.2-1.6 mm., lamina oblong, obtuse, gradually
norrowing into a claw about 1/3 length of petal. Stamens 2.5-3.0
mm Siliqua-pedicels patent-ascending, 7-11 mm long; siliqua 11-17
mm X 0.75 mm, about 16-seeded; septum 1-nerved to about midway.
Seeds 1.2 x 0.5 mm, brown, uniseriate. Figure 9.
Figure 9. Distribution of D.bourgaeana.
Type: Tenerife, Filo de Las Cañadas, 7.7.1855 Bourgeau 1268
(FI, BM isotype).
Other specimens: Canary Islands. Tenerifes between Portillo
and El Cabezón, 2000 m, 15-4-1969 Bramwell 1312; Las Cañadas, La
Fortaleza, 2100 m, 16.7.1969 Bramwell 2102; Las Cañadas de Teide,
Mirador de los Roques, 2000 m, 26.7.1972 Bramwell 3517; Las Caña­das,
Portillo, 1 km along road to Pió, 22.6.1956 Lems 2690; Teide
Cráter, . 7000 ft., 15.5.1970 Mulford 149, 152 (all RNG); Las Caña­das,
Hierba Pajonera, Sept. 1965 Bramwell 45; Las Cañadas, 3-4-1890
Murray s.n.; Anaga, 800 m, 24.4.1855 Perraudiére 11204 (all BM);
Las Cañadas, El Portillo, 200 m, 10.4.1971 Bramwell & Humphries
3383 (RNG, BM); Las Cañadas de Teide, Montaña de las Arenas
Negras, 2000 m, 22.10.1968 Bramwell 262; Filo de Las Cañadas, 7.1.
1855 Bourgeau 1268; Las Cañadas, El Portillo, 20.4.1933 Asplund
864; Las Cañadas, at base of Mt. Teide, 2300 m, 8.5.1969 Okpon
45
DAVID BRAMWELL
Mt. Teide, 2000 m, 3.7.1855 Perraudiére s.n.; Las Cañadas, 3-6-1890
Murray s.n. (all K).
D. bourgaeana is a locally dominant component of the vege-tation
of the subalpine zone of Tenerife between 1800 and 2300 m.
where it occurs on phonolytic rock debris, volcanic sand and scree
etc. in association with Argyranthemum tenerifae, Tolpis wehhii,
Pterocephalus lasiospermus and other locally endemic species.
Morphologically it most resembles D. lemsü but can be seoa-rated
by its markedly decurrent primary leaf-segments with 3-poin-ted
ápices and its patent fruiting pedicels with ascending siliquae.
3. D. leimii Bramwell, Cuad. Bot. Cañar. 17:24 (1973).
Shrub 50-75 cm, branches erect, cortex brown with short, sil-very
pubescence on the younger stems. Leaves 2-pinnatisect, sube-rect,
lanceolate 2-4 (-6) x 0.8-1.0 cm, sessile or shortly petiolate,
densely pubescent with branched hairs only; primary lobes linear
or linear lanceolate, 7.0 x 1.0-1.5 mm, shortly petiolate; secondary
lobes linear^to ovate-lanceolate upto 2 mm, those towards the apex
slightly longer, acute, upper leaves pinnate, sessile; lobes linear-lanceolate,
those towards the base filiform. Inflorescence simule or
sparsely branched, erect, pedicels up to 15 mm with branched and
glandular hairs. Sepáis erecto- patent 3-4 mm, pubescent with glan­dular
and branched hairs. Petáis broadly ovate 5-6 x 3-4 mm, cu­néate
with claw equalling lamina. Stamens 4-5 mm. siliqua pedicels
erect.
O
^
Figure 10. Distribution of D.lemsii.
46
REVISIÓN OF DESCURAINIA IN THE CANARIES
Siliquae 20-35 mm. x 8 mm, torulose, often irregularly cur­vea,
28-to 32- seeded. Seeds ovate, 1.5 mm, hetnut coloured, unise-riate.
Figure 10.
TYPE: Tenerife, Lomo de Pedro Gil, 1800 m. 14-4. 1969 Bramwell
1299 (RNG).
Other specimens: Canary Isiands, Tenerife, Lomo de Pedro
Gil 1800 m. 14.4.1969 Bramwell 1299 (RNG, ISOTYPE): Tenerife
Cumbres de Pedro Gil above Agua Mansa 1600 m, May 1969 Bram-toeJl
1477 (RNG); Tenerife, Nr. Izaña, 200 m. 30.5.1969 Bramwell
2284 (RNG); Tenerife, nr. Fuente de Joco, 1900m, 2.4.1971, Bram­well
& Humphries 3184, (RNG); Montaña Ayesa, 1950 m, 12.11.1965,
Lems 6269 (RNG); Fuente de Joco, 1900 m, 2.2.1966 Lems 6905
(RNG).
D. lemsii is endemic to the higher northem slopes of Tene­rife
at the upper ümit of the pine forest zone between 1700 and
2000 m. It occurs as scattered populations in the open habitats af-forded
where the high montane Pinus canariensis forests merge into
the subalpine Spartocytisus supranubius and Adenoarpus viscosits
scrub. D. lemsii is readily distinguishable from D. bourgaeana by the
absence of decurrent leaf-segments, lack of glandular trichomes on
the leaves and the erect siliqua pedicels. The more dissected leaves,
broader leaf-segments, larger siliquae with more numerous ovate
seeds and petal-claw equal to the lamina sepárate this species from
its nearest relative D. gilva from similar habitats on the island of
La Palma.
4. D. millefolia (Jacq.) Webb & Berth., Phyt. Cañar. 1:73 (1936).
Sinapis millefolia Jacq., Collectanea 1:41 (1786).
Sisymbrium millefolium (Jacq.) Solander, in Aitón hort.
Kew. ed.l, 2:391 (1789).
S, millefoliatum Link., Handb. Gewachk. 2:313 (1831).
Hesperis millefolia O. Ktze., Rev. Gen. Pl. 1:33 (1891).
Branched, woody shrub up to 1 m. Lov/er stem very woody,
glabrous, up to 1 m in diameter. Young branches ascending, terete,
densely leafy, densely pubescent. Leaves petiolate, oblong-elliptical
20-80 mm long (2-) to 3- pinnatisect, with 4-10 pairs of primary seg-ments
and 2-8 pairs of arénate to pinnatipartite secondary segments;
the ultímate lobes lanceolate to ovate, obtuse. Upper leaves shortly
petiolate or sessile, usually 2-pinnatisect with ovate, entire, crenate
47
DAVID BRAMWELL
or pinnatifid tobes. Inflorescences dense, congested with 30—^ca.lOO
ftowers, etongating after anthesis. Pedicels 5-12 mm tong, pubes-ent
with branched and glandular hairs. Sepáis erecto-patent, 3-4 mm,
palé yelltew, glandular hairy. Petáis large, 5.0-6.5 x 2.0-3.0 mm; la­mina
shortly ovate, obtuse, occasionally lobed; claw equalling lami­na.
Stamens 3.5-5.0 mm Siliqua pedicels 6-17 mm irregularly outs-preading
or ascending. Siliquae 10-25 x 1.0-1.7 mm, 10-to 22-seeded,
torulose; seeds ovate-triangular, about 1 mm long, reddish-brown,
uniseriate or occasionally biseriate. Figure 11.
O
< >
Figure 11. Distribution of D.millefoUa.
Type: Not traced, Poiret in Lamarck's Encyl. Meth. Bot. 4 p.
345 (1797) States that Jacquin cultivated this species but no speci-men
has been traced which could be attributed to Jacquin. There
is, however, an illustration in Jacquin's le. Pl. Rar. l:t 27 which
could serve as the type if no specimen comes to light.
Other specimens: Canary Islands. Tenerife: Mñas. de Teño,
Roque de Fraile, 150 m, 16-10-68, Bramwell 225; Cuevas Negras de
Los Silos, 400 m, 29-10-68; Bramwell 312; San Juan de la Rambla,
200 m, 9-11-69, Bramwell 366; Mñas. de Teño, Cumbre de Masca,
1000 m, 12-1-69, Bramwell 512; Icod el Alto in Barranco Ruiz, 650
m, 20.1.69, Bramwell 542; Bco. del Infierno, Adeje, 600 m, 10.3.69,
Bramwell 932; Mñas. de Teño, Valle de Masca above the village of
Masca, 500 m, 26.4.69 Bramwell 1394; Sierra Anaga below Cruz de
Taganana, 500 m, 21.5.69, Bramwell 1532; Bco. del Fraile, Guía de
Isora, 400 m, 26.5.69, Bramwell 1692; Bco. de Ruiz, 650 m, 22.6.69,
Bramwell 1756; Punta de Teño, between Roque del Fraile and El
48
REVISIÓN OF DESCURAINIA IN THE CANARIES
Faro, 50-150 m, 5.4.1971, Bramwell & Humphries 3276 (all RNG);
Feb. 1845, Bourgeau 2; E: of Puerto de la Cruz, 20 m, 23.8,1971,
Chicken 8; Icod, La Guaricha, 400, 3.9.1971, Chicken 134; Icod el
Alto, 30.12.1857 Lowe Ten. 148; Güimar, Bco. del Anaga, April
1855, Murray s.n.; Below Icod de los Vinos, 6.6.1890, Murray s.n.
(all BM); La Corona, 3.10.1927, Czeezott 389; Orotava, 9.1.1927,
Gram 54; 1782, Masson s.n.; Bajamar, 30.5.1899, Murray s.n.; Bco,
de los Silos, 3.5.1902, Murray s.n.; Icod, March 1933, Trethelly 142
(all K.).
Gomera: 4 km along road from San Sebastián to Benchiji-gua,
11.3.73, Aldridge 1167; road from San Sebastián to Lomo Fra­goso,
12.3.73, Aldridge 1217; Bco. de Valle Gran Rey, 600 m, 20.12.
1968, Bramwell 471 (all RNG); San Sebastián, 6.2.1858, Lowe G. 129
(BM).
La Palma: El Time, 29.3.1973, Aldridge 1450; La Cumbreci-ta,
1500 m, 9.6.1969, Bramwell 1879; terraces near El Paso, 15.4.1971,
Bramwell & Humphries )441. (all RNG); El Río, S. Cruz, June
1892, Murray s.n. (BM); Bco. del Río above aquaduct, 2.6.1913,
Sprague & Hutchinson 199; La Caldera, El Capadero, 13.6.1913,
Sprague & Hutchinson 408 (all K).
D. m,illefolia is a locally frequent species of the lower zone of
Tenerife, La Palma and La Gomera (50-1200 m) found on cliffs,
rocks, walls etc., usually in partial shade. It is a very variable spe-cie
sin terms of leaf-division and fruit length. Individuáis with
only 2-pinnatisect lower leaves have been described as var. sabina-
Figure 12. Distribution of D. gilva.
49
DAVID BRAMWELL
lis O.E. Schulz but in cultivation the character is not constant. Fma.
hrachycarpa Bornm. and var. macrocarpa Pitard cannot be satis-factorily
delimited as they fall within the normal variation in fruit-size
of most populations.
5. D. gilva Svent., Bol. Inst. Nac. Inv. Agron. 13:20 (1953).
Shrub up to 50 cm, strongly branched at base; cortex slight-iy
pubescent. Leaves sessile, erecto-arcuate, lanceolate-elliptical,
20-40 X 7-15 mm., 2-pinnatifid, pubescent the segments linear suba-cute.
Inflorescences simple or laxly branched, branches sub-erect.
Pedicels about 4 mm, densely pubescent. Sepáis erect, about
2 mm, fioccose-tomentose. Petáis 4.0 x 2.0 mm elliptical-cuneate
with a short claw. Stamens 2 mm. Fruiting branches more or less
arcuate. Siliquae 15-20 x 1.0 mm. 16-to 24- seeded. Seeds 1.0 - 1.5
mm., obiong, compressed, chestnut-coloured, the surface finely pa-pillate.
TYPE: Junonia Major (La Palma) in cacumine montis ad
oram magni crateris "Gran Caldera" nuncupati ad 2.000 m supra
mare, 21 Maii 1949. E. R. Sventenius (TEÑE).
Other Specimens: La Palma, Tijarafe, 1700 m. E. R. Svente­nius
13.10.1949 (JCV).
D. gilva is endemic to the high mountains of the rim of the
Caldera de Taburiente in the N. Central región of La Palma where
it is locally frequent. It occupies open sunny clearings towards the
upper limits of the pine forest zone between 1600 and 2000 m. It
is morphologically similar to D. lemsii and D. hourgaeana and can
be considered as a local vicariant of the latter. Very few specimens
are available for consultation in herbaria but living material origi-nating
from the type locality and cultivated in the Jardín Botánico
"Viera y Clavijo" has been studied.
6. D. preauxiana (Webb) Webb ex O.E. Schulz, in Engler Pflan-zenr.
105:344 (1924).
Sisymbrium, preaiujcianum Webb, An. Sci. Nat. Bot. 2 ser. 13:
137 (1840).
D. preauxiana Webb ex Christ, Engl. Bot. Jahrb. 9:90 (1888)
in synon.
Hesperis preauxiana O.Ktze., Rev. Gen. Pl. 2:935 (1891).
50
REVISIÓN OF DESCURAINIA IN THE CANARIES
Sisymhrium briqueta Pitard, in Pitard & Proust Les lies
Cañar. Fl Archip. 101 (1908).
D. preauxiana Webb ex Christ var. hriquetii (Pit.) O.E.
Schulz, Pflanzenr. 105:345 (1924).
Small shrub, woody at base, 60-80 cm, eortex glabrous, whi-tísh.
Leaves petiolate, simple-pinnatisect, 4-10 cm long, covered
with glandular trichomes; the segments linear, to filiform in up to 6
pairs. Upper leaves more or less simple. Inflorescences simple,
crowded at anthesis then elongating in Fruit, 40-to 80- flowered;
pedicels 5 - 8 mm, glandular. Sepáis 3 mm, oblong, erecto-patent.
Petáis 5 mm; lamina ovate, obtuse, gradually narowing to a short
claw. Stamens 3-4 mm. Siliqua pedicels 8-13 mm, sub-erect. Sili-quae
ascending, often irregularly curved, 10 - 17 mm, 18 - to 27 -
see^ied, torulous. Seeds 1.2 mm, oblong, uniseriate or occasionally
biseriate, chestnut coloured. Figure 13.
TYPE: Gran Canaria, Bco. de Amurga leg. Despreáux (Fl).
Other Specimens: Canary Islands. Gran Canaria: Bco. de
Tejeda between Tejeda and La Solana del Chorrillo, 1250 m, 11.5.
1973, Aldridge 1535; central región just below Roque Nublo, 1600
m, 27.3.1969, Bramwell 1055; Bco. de Fataga, 400 m, 30.3.1969,
Bramwell 1179; Bco. de Fataga velow Fataga, 500 m, 21.3.1971,
Bramwell & Humphries 3037; Degollada de Tazartico, 600 - 700 m,
21.3.1971, Bramwell & Humphries 3074 (all RNG); Tejeda, 850 m,
20.4.1936, Brooke 135; Tejeda, 24.5.1897 Gelest s.n.; Lomo de los
Florales (Fataga), 740 m, 20.1.1969, Kunkel 12308 (all BM); bet­ween
Tirajana and Mogan, 10.5.1894, Murray s.n. (BM, K).
O
s?
Figure 13. Distribution of D.preauxiana.
51
DAVID BRAMWELL
D. preauxiana is endemic to the island of Gran Canaria whe-re
it is relatively common in the interior región on cliffs between 400
and 1800 m. It is very variable in leaf-shape, size and in ñower-si-ze
and several forms and varieties have been described. Variation
is. however, reticulate without a consistent pattern and it seems
appropiate simply to recognise a single polymorphic species withouit
delimiting infraspecific taxa. Specimens with large leaves and flo-wers
described as S. briqueta by Pitard (1908) fit into the nor­mal
variation pattern of D. preauxiana from shady or more humid
habitats and despite Lems'(Lems, 1960) suggestion that S. hriquetii
Pitard is conspeciñc with D. artemisoides it is here included in D.
preauxiana. Holzpfel in Lems & Holzapfel (1974) corrects Lems'ori-ginal
error and regards S. hriquetii as part of Descurainia preau­xiana.
7. D. artemisoides Svent., Bol. Inst. Nac. Inv. Agron. 28:15 (1953).
Shrub up to 80 cm; stems erect, the young tips fomentóse,
cortex greyish, splitting when older. Leaves ovate, 2-pinnatisect,
shortly petiolate to sessile, densely fomentóse, with branched hairs,
primary segments 6-10 pairs, ovafe-lanceolafe, shortly petiolate, se-
O
Figure 14. Distribution of D.artemisoides.
condary segments ellipfic-spathulafe, decurrent, the apical segment
larger, lanceolate. Upper leaves pinnate with up to 4 pairs of seg­ments.
Inflorescence simple or branched. Pedicels 10-15 mm, erecto-arcuate,
fomentóse with glandular and branched hairs. Sepáis
oblong-spathulafe, more or less pafent, 3 mm, palé yellow. Petáis
fwice as long as sepáis 5.0-6.0 x 1.7-3.0 mm; lamina ovate and cu-
52
REVISIÓN OF DESCURAINIA IN THE CANARIES
neate to a claw almost equal to lamina. Siliquae densely clustered
in fruit. 15-20 x 1.0 mm, about 20- seeded, th eseeds 3-angled, 2 mm
long, compressed-semi-lunar, brown, uni- to biseriate.
TYPE: Canaria Magna; supra pagum Goyedrae ad 700 m su-pra
mare, 2 aprilis 1947 E. R. Sventenius sn. (TEÑE).
Other Specimens: Canary Islands, Gran Canaria: Los Be-rrazales,
Agaete, 500 m 29-3-1969 Bramwell 1155 (RNG), Agaete,
barranco de los Berrazales 450 m 19-3-1969 Bramwell 1155 a (RNG),
Berrazales, Agaete 600 m 7-2-1966, Kunkel 12457 (BM).
A local endemic of the Goyedra Massif on the W. side of
Gran Canaria. D. artemisoides is locally frequent in shady ravines
and in the shade of N. W. facing cliffs.
REFERENCES
BAKER, H.G. 1959.—Reproductive Methods as FactoTS m Speciation in Flowering Plants.
Cold Spring Harb. Symp. Quant. Biol. 24: 177-190.
BALDWIN, J.T., J.M. CAMPBELL 1940.-JChromosomes of Oruciferae. 1. Descurainia.
Amer. Jour. Bot. 27, 10: 915-918.
BORGEN, L. 1969.—Ohromosome numbors of vacular pJants from the Canary Islands, with
special reference to the ocourence of poilyploidy. Nytt. Mag. Bot. 16, 8Í-121.
BRAMWELL, D. 1973.—New species of Cruciferae from the Canary Islands. Cuad. Bot.
Cañar. 17: 19-26
CHRIST, H. 1888.—Spicilegium canariense. Engl. Bot. Jahrb. 9: 90
DETLING, L.E. 1939.—A Revisión of the North American species of Descurainia. Am.
Midi. Nat. 22, 481-520.
LARSEN, K. 1960. Cytological and experimental studies on the flowering plants of the Ca­nary
Islands. K. Danske Videnskab. Selskab. Biol. Skr. 11, 3: 1-60.
LEMS, K. 1960.—^Floristic Botany of the Canary Islands. Sarracenia 5: 1-94.
LEMS, K. & HOLZAFFEL, C. 1974.—Flora of tihe Canary Islands: The Cruciferae, tfae
Crassulaceae and the Ferns at their allies. Ans. INIA ser. Prod. veg. 4: 165-273.
PITARD, J. & L. PROUST 1908.—Les lies Canaries. Flore del Arohipel. París.
SCHULZ, O.E. 1924.^Cruciferae — Sisymbrieae Das Pflanzenreich 105, Heft 86 Im Ver-lag
von H.R. Engelmann. Weinheim/Bergstr.
SVENTENIUS, E.R. 1953.—Specilegium Canariense. Boln. Inst. nac. Invest. agron., Madr.,
13: 15-20.
WEBB, P.B. & BERTHELOT 1836 — 1850.—Histoire naturelle des Ees Canaries. Tome 3.
Phytographia Canariensis sect. 1. París.
53