ACCUMBENT AND INCUMBENT COTYLEDONS 37 



remaining the same, it is better that the radicle should be 

 accumbent ; while, on the other hand, in a thicker or globular 

 seed, as in fig. 71, the incumbent arrangement is most con- 

 venient. In fact we find that in groups, such as the Arabideae, 

 where the seeds are as a rule compressed, the radicle is almost 

 always accumbent ; while in incumbent groups, such as the 

 Sisymbriese, they are, on the contrary, more or less turgid. 



FIG. 75. Seedling of Bryonia laciniosa. Half nat. size. 



As an actual example of an incumbent form I give Hesperis 

 matronalis (figs. 71 and 72), and of an accumbent, Cheir- 

 anthus Cheiri (figs. 73 and 74). 



PETIOLES. 



The cotyledons are sometimes sessile, as in Acer (fig. 9), 

 Hippophae (fig. 14), Hakea (fig. 21), Clitoria (fig. 27); 

 sometimes supported on petioles, which in many cases, as in 

 Microloma (fig. 29), attain a considerable length. 



Occasionally we meet with both sessile and petioled coty- 



