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, 

 being characterized by the 

 first kind, and dicotyls by 

 the second. 



172. Pinnate and pahnate veining. — 

 Next, compare a leaf of the canna, calla lily, 

 or any kind of arum, with 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 pinnatehj, 

 or feather veined, as in Figs. 206, 207. In fig. 207. — Pin- 

 the cotton, maple, ivy, etc., on the other lately paraiici- 



•11 ri- veined loaf of calla 



hand, the petiole breaks up at the base 01 the my (After Gray). 



Fio. 205. — Par- 

 allel-veined leaf of 

 lily of the valley 

 (Afte)- Gray). 



Fig. 20G. — Net- 

 veined leaf of a wil- 

 low. 



