Silene dewinteri , a new species of the Caryopliyllaceae from the south-western Cape

A new species of Silene, S. dewinteri Bocquet, is described from the sand-dunes of the coastal region of the south-western Cape. The species is closely related to S. crassifolia L. and S. clandestina Jacq.


IN TRO D U C TIO N
During the course of a journey undertaken to collect material for a revision of the South African species of the genus Silene, I had the opportunity of collecting extensively in the region of Cape Town.One of the localities visited was the coastal area in the vicinity of Table View, 18 km north of Cape Town.This is one of the localities often cited by Ecklon and Zeyher in their " Enumeratio'' (1834) under the name of " Rietvalley" or " Riedvalley".I was trying to trace an elusive species listed as " Silene Constantia" in Ecklon and Zeyher's work-a species closely related to S. clandestina Jacq.I found the plant growing in popu lations on the sand dunes of the coast between Table View and Melkbosstrand mostly side by side with populations of S. crassifolia L.
The plant is an annual species with a spreading habit, fleshy leaves, thickened calyx and protruding calyx nerves.Unfortunately, the name S. constantia cannot be given to this species, because it applies to another species (see p.000 under Nomenclature).I therefore name the plant S. dewinteri in honour of Dr B. de Winter, Director of the Botanical Research Institute, Pretoria.
Flowering times are different for the two species: S. dewinteri flowers in August and September, and S. crassifolia from October to January.A biological barrier therefore exists between the two species.No trace of introgression or morphologically intermediate specimens was observed in the localities visited.S. dewinteri seems to be equally distinct from S. clandestina.The latter species is also an annual, but is not found as near the sea shore as S. dewinteri.S. dewinteri seems to be strictly limited to the immediate proximity of the sea.

Taxonomy. S. dewinteri has rarely been collected
, probably because the more common S. crassifolia occurs in the same localities and depauperate forms of the perennial S. crassifolia can easily be mistaken for the annual S. dewinteri.
The affinities are clear: S. dewinteri is closely allied to both S. clandestina and S. crassifolia, but can be distinguished as follows: (a) from S. crassifolia by its annual character, smaller calyx and thin root: S. crassifolia always has, even in the youngest stages, a thickened root; the older specimens build up a nearly bulbous root.var.angustifolia Bartling (1832)  Cytology.Chromosome counts on flower buds of cultivated material yielded the number n=12.Material: Bocquet 17881; Carnoy-acetocarmine treat ment; 10 counts from 3 slides and 2 buds.Fig. 4 shows an anaphase; the chromosomes are small, but not as contracted as they usually are in meiotic phases of Silene species.In most Silene species they appear at this stage as more or less isodiametric spots.

A CK N O W LED G EM EN TS
This work has been carried out with the aid of a grant from the Societe helvetique des Sciences Naturelles and assistance from the ETH-administration.I thank these authorities.

U IT T R E K S E L
'n Nuwe species van Silene, S. dewinteri Bocquet, word beskryf van die sandduine van die kusstreek van die suidwestelike Kaap.Die species is naverwant aan S. crassifolia L. en S. clandestina Jacq.

OBSERVATIONS 1 .
Ecology, biology.S. dewinteri is an annual grow ing scattered in the half-colonized parts of coastal dunes, in open localities on semi-stabilized sand.It is often accompanied by S. crassifolia, a perennial (b) from S. clandestina by the thicker leaves, clavate, broader and very fleshy calyx, as well as the spreading habit.Material was cultivated in Switzer land under glass from seeds of the three populations Bocquet 17818, 17774 and 17881.The plants are some what more flaccid and the leaves bigger, but the essen tial characters can be recognized, namely the thick ness of leaves, spreading habit and broader calyx with bulging nerves.3. Nomenclature.Ecklon and Zeyher intended describing our plant as a new species under the name of S. constantia (the specific epithet refers to Constantia, a suburb of Cape Town).The description, locali ties and herbarium material agree with S. dewinteri However, Ecklon and Zeyher cited S. crassifolia L F i g .3.-Transect of the Bloubergstrand locality (Bocquet 17781; 17783).1, strand; 2, distribution o f S. crassifolia on the undulating ground in front of the coastal dune (sparsely colonized and unstable sand); 3, S. dewinteri, at the foot of the coastal dune (semi fixed and half-colonized sand).