22 MORPHOLOGY 



35. This same anomaly, as to the development of long stalks 

 to the cotyledons and their union into a stem-like body, occurs in 

 various species of Larkspur (notably in the Californian Delphin- 

 ium nudicaule) ; but in these the cotyledons develop into a pair 

 of efficient green leaves. 



45 



36. A similar elongation of petioles of the cotyledons, but 

 without any union, occurs in a species of Morning Glory of the 

 plains beyond the Mississippi (Ipomcaa leptophylla) ; the leaf- 

 like cotyledons coming up on their long stalks separately from 

 the ground (Fig. 45) ; the developed plumule rising some 

 time afterward between them. Compare this with the ordinary 

 species (25, Fig. 15, 16, 25), and note that the difference is merely 

 that the caulicle in the common Morning Glory elongates and the 

 petioles of the cotyledons remain short. 



37. In all instances thus far a single primary root so regularly 

 develops from the lower end of the axis of the embryo (variously 

 named radicle or caulicle) , and forms such a direct downward 



FIG. 45. Germination of Ipomoea leptophylla; the caulicle not developing, the 

 plumule and the petioled cotyledons rise from underground. Dotted line marks the 

 level of the soil. 



FIG. 46. Embryo of a Pumpkin, the cotyledons separated. 47. Same germinated; 

 a cluster of roots from the base of caulicle. . 



