64 :©otanB 



veins. Some of these veins are coarser and stronger 

 than others, as for example, those which expand in 

 the large side-lobes of maple and oak leaves ; other 

 veins are as fine as spider's web. Every student of 

 botany should make studies in venation, by soaking 

 leaves until the green part has decayed, then lajang 

 them on black cloth, and brushing the pulp away 

 gently with a fine brush, when perfect specimens of 

 frame-work will remain. 



The form of the leaf depends upon the woody 

 frame-work. Upon it is spread the green pulp called 

 parenchyma. This is composed of cells, while the 

 woody frame-work is formed of expanded or modi- 

 fied cells, called vessels. Over all the leaf is laid a 

 thin, transparent skin, named an epidermis, which 

 covers the footstalk, stipules, and all leaf append- 

 ages. Usually the epidermis on tlie upper side is 

 more glossy and of a finer texture than on the lower 

 surface, which is softer and more porous. As we 

 shall see, there is good reason for this. 



All plants which have one cotjdedon have hollow 

 reed-like stems, and their leaves have parallel veins ; 

 that is, veins running side by side, without branch- 

 ings ; grasses, grains, rushes, lilies, palms, bamboos, 

 are of this one-cotyledoned, parallel-veined family. 



There are two different kinds of i>arallel venation. 

 There may ])e a mid-rib, and the veins run from this 



