THE LEAF 



155 



coloring fluid a short time before the lesson begins. The leafstalks of 

 celery and plantain are excellent for showing the relation between the leaf 

 veins and vascular system of the plant. 



171. Parallel and net veining. Compare a leaf of the 

 wandering Jew, lily, or any kind of grass, with one of grape, 

 ivy, or willow. Hold each up to the light, 

 and note the veins or little threads of woody 

 substance that run through it. Make a draw- 

 ing of each so as to show plainly the direc- 

 tion and manner of veining. Write under the 

 first, parallel-veined, and under the second, 

 net-veined. This distinction of leaves into 



parallel and net- veined cor- 



responds with the two great 



classes into which seed-bear- 



ing plants are divided, mon- 



ocotyls, as a general thing, FlG . 205. Par- 



being characterized by the aUei-veined leaf of 



lily of the valley 



first kind, and dicotyls by (After GRAY). 

 the second. 



172. Pinnate and palmate veining. - 



FIG. 206. Net- Next, compare a leaf of the canna, calla lily, 



veined leaf of a wil- Qr an y k m( J Q f arum , W ith One of the elm, 



peach, cherry, etc. What resemblances do 

 you notice between the two ? What differ- 

 ences? Which is parallel- veined and which 

 is net-veined ? Make a drawing of each, and 

 compare with the first two. Notice that in 

 leaves of this kind, the petiole is continued 

 in a large central vein, called the midrib, 

 from which the secondary veins branch off 

 on either side like the pinnae of a feather; 

 whence such leaves are said to be pinnately, 

 or feather veined, as in Figs. 206, 207. In 

 the cotton, maple, ivy, etc., on the other 

 hand, the petiole breaks up at the base of the 



FIG. 207. Pi n- 

 nateiy paraiiei- 



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