THE LEAVES OF VASCULAR PLANTS. 253 



to have curved nerves, peculiar to the class of Monoco- 

 tyledons, and they serve also to confirm this fundamental 

 distinction. 



We come thus to the second of the great divisions, — 

 that of leaves with nerves curved at their base, or 

 CuRViNERVED ones. Among these we ought to dis- 

 tinguish two classes, viz. those with Converging 

 nerves, and those with Diverging ones. 



In the first the nerves are sometimes curved through- 

 out their whole length, which causes the limb to be 

 oval or round, as in Hemerocallis, &c. ; sometimes 

 slightly curved at their base, and straight, parallel, or 

 slightly convei'ging at their apex, as is seen in the 

 Graminece. In all those plants, which represent among 

 phanerogamous Monocotyledons nearly what are the 

 palminerved leaves among Dicotyledons, the nerves 

 spring from the top of the petiole in great numbers, and 

 are the closer to each other the nearer they are to the 

 middle. Most frequently they are so close towards 

 the centre that they perform the part of a longitudinal 

 nerve. When the nerves which spring from the base 

 are very near together, they are generally very small, 

 and perfectly simple ; when they are more distant they 

 are also thicker, and tend a little to ramify laterally, as 

 is seen in Dioscorea, Sinilax, &c. 



Diverging curvinerved leaves present precisely the 

 opposite organization. The nerves united in the petiole 

 form a very thick bundle, and the formation of the limb 

 takes place by the lateral fibres of the petiole diverging, 

 at a certain point, on both sides, under the form of 

 little pinnate veins, which by their junction form an 

 oval limb, with small, parallel, and simple nerves. 

 In proportion as this separation of the lateral fibres 

 takes place to form the limb, in proportion likewise the 

 central bundle diminishes in thickness, until it finally 



