126 



PLANT LIFE. 



There may be a main rib, from wliose flanks arise at regular 

 intervals a series of lateral branches which may themselves 



Fig, 148. Fig. 149. 



Fig. 147. — A palnuitely branclied (conipi.und) leaf of horse chestnut. About otie-tiftli 



natural size. — Alter Bessey. 

 Fig. 14S. — A palmately branched (compound) leaf. — After Bessey. 

 Fig. 14CJ. — Leaflets of maidenhair fern showing dichotomuus branching of veinlets, 



which end free. Natural size. — After Ettingshausen. 



again be branched in various ways. Such a leaf is said to be 

 pinnately veined (iigs. 13S, 151, 153). Or (2) from the top 

 of the petiole several large ribs of almost equal strength may 

 be given off. Such venation is pahnate (figs. 150, 152). 

 These may be parallel (fig. 150) or radiate (fig. 152). 



The distribution of the small ^'ei^s or nerves shows three 

 types. They may either (1) connect with each other so as 

 to form an irregular meshed network (fig. 151); or, (2) leav- 

 ing a rib nearly at right angles, they may run parallel with 

 each otlier to join another large vein ; or (3) they may leave 



