224 ON SEEDLINGS 



Seedlings. Oblong and ovate cotyledons predominate in 

 this Order, but oval and subrotund ones are also met with. 

 Those of Calotropis gigantea (fig. 518) are broadly oblong, 

 obtuse, and entire, with an incurved venation similar to that 

 of the first pair of leaves which are more elliptic in outline. 

 Asclepias obtusifolia, Tylophora asthmatica, and Gyrnnolaema 

 viride agree pretty closely with this type in having oblong, 

 obtuse cotyledons with a venation resembling that of the 

 primary leaves ; they vary somewhat in width, but are always 

 wider than the first pair of leaves. The first pair in Tylo- 

 phora asthmatica are oblong-lanceolate, while the first five 

 pairs of Gymnolaema viride are narrowly lanceolate and acute, 

 or even acuminate. The cotyledons of Schubertia grandiflora 

 are shortly oblong, obtuse, and of the same width as the ovate 

 first pair of leaves. 



A slightly different type of seedling is met with in Gompho- 

 carpus campanulatus (fig. 517), which by its slender stems and 

 long internodes shows a tendency to climb. The cotyledons 

 are oblong with an incurved venation like that of the first 

 three pairs of leaves which are ovate or subcordate and hairy. 

 The cotyledons of a species of Microloma (fig. 516) are also 

 oblong with incurved nerves, but they are notable for the great 

 length of their petioles. The latter characteristic is due to 

 the unusual shortening of the hypocotyl and probably to the 

 nature of the situation in which the plant grows, neces- 

 sitating the lengthening of the petioles in order to bring the 

 lamina up to the light. The two first pairs of leaves are 

 small and scale-Like, while the succeeding three are Linear- 

 lanceolate with a few alternate, ascending, indistinct nerves 

 on each side of the more evident midrib. 



The ovate type of cotyledons is represented by Periploca 

 laevigata where they are broader than the primary leaves 

 with a similar venation. The first three pairs of leaves are 

 ovate-elliptic. Some succulent types of seedlings have ovate 

 cotyledons broader and larger than the leaves that follow 

 them. Those of Sarcostemma brevistigma (fig. 519) are 

 oblong-ovate and sessile. The first two pairs of leaves are 

 ovate, but they are reduced to minute, scale-Like organs. 

 This plant like the species of Stapelia is notable for the stout 



