sin J. LUBBOCK — PnXTOBIOLOGlCAL OBSERTATIOyS. 385 



m 



appear in this and other cases, after the emergence of the cotyle- 

 don, to stop its growth at that paint, and thus to produce the 



emargination. 



S^necio 



dons. In some, however, as in_^. eruc(Bf alius ^ they are emarginate. 

 Even here, however, they are at first entire (fig. 115), and the 

 emargination does not make its appearance until after germi- 

 nation, when the cotyledons gradually become much widened 

 (fig. 116). In fact, Senecio squaUdicSj S. viscosus^ S, vulgaris, 



Fig. 115. Fig. IIG. 



Fig. 115. Young seedling of Senecio eruccefoUus, 

 Fig. IIG. Ditto, a few days older. 



4 



&c. have the cotyledons narrow and entire ; while in ^S'. erucce- 

 foUus and S. Cruentus, where they grow more in width than 

 in length, they become emarginate. Among other cases where 

 the cotyledons are at first entire, but after germination become 

 emarginate, may be mentioned some species of Lithospermum. 



Bryonia laciniosa (fig. 92) also has the cotyledons emarginate, 

 "v\hiie in Bryonia dioica (fig. 93) they are entire. They are, how- 

 ever, originally entire in both cases, and the emargination in 

 B. laciniosa is due to the fact that in that species the cotyledons 

 grow much more than in B. dioica. There is no great difference 

 in size between the seeds, those of B. laciniosa being perhaps 

 one tenth larger. On the other hand, the cotyledons of B, 

 laciniosa attain a length three times greater than those of B. 

 dioica, as shown in the figures (6g3. 92 & 93). In the genus 

 Tacsonia, a^^^ain, the cotyledons are entire in T. Van-Volxenii 

 and J\ Lesclienaultii, and emarginate in T. ignea. Here also, 

 however, they are at first entire, and only become emarginate 

 after leaving the seed. 



Divided Cotyledons, 



The genus Pterocarya has very curious cotyledons (fig, 11), 

 due to a cause entirely diflferent from any of those we have 

 considered hitherto. 



