3GA 



SIR J. LUEBOCK: PKYTOBIOLOGrCAL OBSEUYATIOXS. 



seed is ovate, oblu][uely pointed, glabrous, plano-convex, laterally 



much compressed, placed edgeways on tlie placenta, and tlie coty- 

 ledons lie parallel to the flattened axis of the seed. In other 

 eases the seeds are still more flattened, as in Ailantltus, Passijlora, 

 Coha^a, SfepJianofis, etc. 



The Composit^e generally have narrow cotyledons. In Mos- 

 clifiria^ however, they are somewhat broader, the seed (fig. 5C) 

 being obovoid, with the cotyledons Iving the broad way. 



A 



Fig. 57. 



Fig. .5G 



B 



LAH 



SAIL 



R 



B 



Fig. 66. Moscharia pinnatifida. A. Longitudinal section of seed, X 8. 



Transverse section of seed, X 8. a a, auricles. 



Fig. 67. Euellia longjfoUa, A. Longitudinal section of seed, X 10. B. Trans- 



'Verse section of seed, x 10. FH, fringe of liuirs; LA?;, larger, 

 and SA;^, smaller auricle. 



In many cases, seeds of the same shape produce cotyledons 

 of very different form. 



Compare together, for instance, TUellia (fig. IG seedling, and 

 fig. 57 seed) and Cerastium (fig. 23 seedling, and fig. 58 seed). 

 Both have compressed, nearly orbicular seeds, but in Buellia 

 the cotyledons are broad, in the Chickweed they are narrow. If, 

 however, we make sections of the seeds, the cause of this diff'erence 

 becomes obvious, because in one (fig. 57) the cotyledons lie parallel, 

 in the other (fig. 58) transverse, to the seed. 



The form of the cotyledons often diflers greatly even in the 

 same family. 



The Caryophyllacea), the family to which tlie Pink belongs, 

 aff'ord an interesting illustration. The cotyledons are placed 

 with their backs to the placenta, and in most species are narrow, 

 as in Cerasfium (fig. 23). In some of them, howcA'er, such 



as the Pink itself (DianihuSj 

 wide. 



) 



