EMARGINATE COTYLEDONS 



47 



tions. In the former the cotyledons commence with an entire 

 end (fig. 91), and subsequently, not as a rule till they have 

 left the seed, become emarginate (fig. 92) ; in (Enothera 

 Lindleyana, on the contrary, the cotyledons are at first emar- 

 ginate, but gradually cease to be so. The embryo gradually 

 appropriates all the endosperm, but the supply being largest 

 at the wider end of the seed, this is the last part to be 

 absorbed. In neither of these cases does the emargination 

 appear to be directly due to the structure of the seed, nor to 



FIG. 91. Young seedling of 

 Oalium Aparine, x 2. 



FIG. 92. Ditto, a few days 

 older, x2. 



be in itself of any advantage to the plant. It seems rather to 

 depend on the conditions of growth. In Galium Aparine the 

 cotyledon terminates in a peculiar gland, 1 which would appear in 

 this and other cases, after the emergence of the cotyledon, to stop 

 its growth at that point, and thus to produce the emargination. 



1 This gland has already been mentioned by Gravis in his work on Urtica 

 dioica (Brussels, 1886), p. 139. He observes that about a dozen small stomata 

 occur on it, while they are entirely absent on the rest of the upper surface. 

 He regards it as a water-gland, ' un organe destine a remedier a 1'exces de 

 tension dans 1'appareil aquifere.' 



