124 



BOTANY 



Leaf of a Dicotyledon. — If we now take up the study of a simple 

 leaf such as the elm, we find that the parts seen in buds of the 

 tulip tree are not always readily found. The petiole or leafstalk 



runs into the blade of the leaf as the 

 midrib. Here it divides to form the 

 network of veins found in the leaves of 

 the dicotyledonous plants.^ 



Leaf of a Monocotyledon. — In the 

 monocotyledons, as in Tradescantia, 

 or in the leaves of a grass, there is no 

 midrib, the leaf being traversed by a 

 number of veins which run lengthwise 

 of the blade and give it the name of 

 parallel-veined leaf.^ 



Drawings should be made to show the 

 parts of a typical simple netted-veined leaf 

 and that of a leaf parallel veined. Both 

 drawings should be natural size and should 

 have all parts labeled. 



Parallel-veined leaf of false 

 Solomon Seal. 



Modification of Blade. — The blade of a leaf may undergo many 

 modifications in different species of plants. It may have almost 

 any shape, from a thin line to 

 an almost circular outline. 

 It may have an almost smooth 

 margin, as in the leaf of the 

 rubber plant (Ficus elastica), 

 or the margin may be more or 

 less deeply indented, as in 

 the tulip, sassafras, and the 

 oak. 



Compound Leaf. — If the 

 margin is so deeply indented 

 that the blade is cut down to 

 the midrib, then each part of 

 the blade is said to be a leaflet, and the whole leaf is compound. 

 In most cases it is easy to distinguish a compound leaf: (1) by 



» See Hunter and Valentine, Manual, pages 39-^2. 2 /j^^.^ page 45= 



Pinnately-compound leaf of rose, showing 

 stipules {St.). 



