270 THE .TOUKNAL OF BOTANY 



usually very close together and completely cover the surface of the 

 ovary, to which they impart a soft villose appearance. 



A more common form of outgrowth is that in which the hasal 

 portion is enlarged and flattened, while the apical cell grows out into 

 a single, stiff, spinous or hair-like process. In some species these 

 apical processes hreak off, leaving the surface of the ovary enclosed in 

 a covering of stiff overlapping scales as seen in Y. EyJesii, where 

 the basal part is large and shield-like in shape (tig. 2). In other 

 species, where the apical outgrowth is shorter and stronger, an ex- 

 tremely harsh echinate covering results. 



Closely allied to this arrangement is the type found in Y. svaveo- 

 lens, where the hasal portion is considerably enlarged but not 

 flattened. Three or more projections arise irregularly from the 

 surface, taking the form of short broad spines ; the whole outgrowth 

 resembles in outline, although not in structure, the stellate hairs of 

 certain Cruciferce and Malvacece (fig. 3). 



Another modification of this form is that characteristic of the 

 species having a viscous surface to the ovary. Here the usual papilla 

 elongates and becomes slightly constricted round the base, while the 

 upper portion is somewhat enlarged. The hypoderinal cells forming 

 the central portion are rich in contents and appear to elaborate 

 a viscous substance, which ultimately breaks through the epidermis 

 and covers the ovary with a viscous layer which dries in irregular 

 masses, imparting a " warty " appearance to the surface of the ovary. 

 This type is characteristic of V. viscosa (fig. 4). 



One species, Y. elegans, found in Natal and possibly in Mada- 

 gascar differs from the other African species in having an ovary 

 which is triangular in cross-section, and has a perfectly smooth 

 surface. In both these respects it resembles many of the New World 

 species. 



It should be noted that the term " hair " as used in this paper is 

 not confined to an epidermal outgrowth. 



Key to Afkican Species. 



Series I. Ovary covered with soft long hairs. 



Leaves filiform 1. V. Hildehrandtii. 



Leaves linear. 



Leaves 10-15 cms. long, densely villose ; 



peduncles 7'5-10 cms. long 2. Y. villosa. 



Leaves 12-40 cms. long, pubescent ; 



peduncles 11-17 cms. long 3. Y. Monroi. 



Leaves 125-15 cms. long, upper surface 

 glabrous, lower slightly hairy ; pe- 

 duncles 7 '5-10 cms. long 4. V. viulacea. 



Series II. Ovary covered ivith stiff hairs. 



* Leaves glabrous ; ovary covered with bristles. 



Margin bearing short bristles. Leaves 



7"5-l0cnis. long; perianth-segments 



