398 Sm J. LTJBBOCK— PHTTOBIOLOGICAL OBSEIlTATIO:^S. 



cotyledons), no less than 25, or as much as 18| percent., differed 

 from the type, aud had this character more or less imperfectly 

 developed. Under cultiyation the seedlings o^ Primula sinensis 

 often have one of the cotyledons deeply bifid ; in one lot of 

 seedlings this was the case with, for instance, over 20 per cent. 



of the plants. 



In Foterium Sanguisorla the calyx-tuhe generally contains one, 

 "but sometimes two or even three achenes. In Hanimculus, occa- 



sionall}^ the petioles of the cotyledons are conn'ate. 



In (Enoiliera the cotyledons are either straight, or wath one or 

 hoth involute. Irmisch states that the cotyledons of jC'/i?;^^//^ 

 rccla^ which are usually aerial, sometimes remain below ground; 

 ■while the reverse is the case in -3/i?Z/Y^/6^, and, according to Winkler, 

 in Bentaria and Mercurialis, for the cotyledons, wliicli are 

 generally fleshy and subterranean, sometimes rise above ground 

 and form small green leaves* 



Many species occasionally have one or both cotyledons divided*. 



In Jiheum the cotyledons are generally parallel, but in some 

 cases one of them is placed more or less obliquely with reference 

 to the other. 



In Fagopyritm the position and arrangement of the cotyledons 

 in the seed vary greatly. The cotyledons are turned about 

 after striking into an angle of the seed, and then, following the 

 testa, assume very various positions. In Carum carvi the coty- 

 ledons sometimes have their backs to the axis of the fruit, and 

 sometimes their edges, while at others they are oblique. 



In Cheiranthus pi/gmcens the cotyledons are said to be sometimes 

 accumbent, sometimes incumbent, and straight or convolute, even 

 in the same pod. 



It would be easy to multiply such cases, but I will only 

 mention one more, in which I will venture to su^r^rest a reason 



^o . . 



for the variation. In Acer (fig. 133, i), the embryo origi- 

 nates in a short tubula^ prolongation of the micropyle, and 

 is at first straight with an extremely short turbinate radicle, 

 and ovate obtuse, closely adpressed cotyledons. As growth 

 continues the embryo extends itself along the lower side of the 

 seed, and curves with it, becoming gradually lanceolate, or oblong 

 lanceolate (fig. 133, 2). "When the cotvledons have reached the 

 upper, narrow end of the seed, the curvature of the wall turns 



* See Goebel, Grundziige Syst. Spec. Pflanzeu Morphologie, p. 505. 



