SEEDLINGS. 



175 



which would arise if a linear leaf were gradually widened at the 

 base ; and I have pointed out that in many species with palmate 

 leaves — for instance, species of Passiflora, Cephalandra, Hibiscus, 

 etc. — the first, or few first leaves, are entire, and more or less 

 cordate. The cordate form, then, appears to be the early, the 

 palmate the later form. But how has the palmate form arisen ? 



" The origin is, perhaps, connected with the manner in which 

 the leaves are folded up, more or less like a fan, in the bud, so as 

 to save space. Another advantage, perhaps, is that the cordate 

 leaves with veins following the curvature of the leaf, as, for 

 instance, in Tamus, Fig. 33, the vascular bundles pursue necess- 

 arily a curved course ; while in palmate leaves, as in Acer, 

 Fig. 34, the veins are straight, and it is clearly an advantage that 

 the main channels which convey the nutritive fluid should hold a 

 direct course." 



I^ig- 35- — Seedling of Fcenic- 

 ulum vulgare, half nat. size. 



Fig. 36. — Seedling of Ceratocephuhis 

 fulcaltcs, nat. size. The numerals in- 

 dicate the successive leaves. 



We now turn to the Forms of Cotyledons, and are told that 



