ORGANS OF NrTEITIOX. 



147 



from which, however, they may be at once distingiiished by 

 their ribs being connected by branching veins. 



2. Varieties of Parallel Venation. 



The term parallel- veined is not strictly applicable in all cases, 

 for it frequently happens that the veins are radiate, but from the 

 difficulty of finding a name which will comprise all the modifica- 

 tions to which such leaves are liable, it must be understood that 

 we apply the term parallel- veined to all leaves in which the main 

 veins are more or less parallel and simply connected by im- 

 branched veinlets. We distinguish two varieties of parallel ve- 

 nation. 



1. Straight-veined. — In this variety the veins either proceed 

 in a parallel direction from the base to the apex of the lamina, 

 to which point they converge more or less {fig. 290), as in the 

 ordinary ribbed variety of reticulated leaves already noticed, 

 and are connected by simple unbranched veinlets ; or they diverge 

 from each other towards the circumference of the blade {fig. 291), 



Fig. 290. 



Fig. 291. 



Fig. 290. Leaf showing the variety of parallel venation called straight. 



veined. Fig. 291. Straight-veined variety of parallel venation, as seen 



in the leaf of the Fan Palm {Cliamoerops). 



as in the radiated-veined variety of reticulated leaves. The 

 leaves of Grasses, Lilies, and the common Flag, may be taken 

 as examples of the first modification ; and those of the Palms 

 of the second. 



2. Curve-vei7icd. — In leaves presenting this variety we have a 

 prominent midrib, as in the feather-veined variety of reticulated 

 venation, which gives off from each of its sides along its whole 

 length other veins, which proceed in a parallel direction towards, 

 and lose themselves in, the margins {figs. 292 and 285, b). These 

 l2 



