THE VENATION OF THE SPECIES OF SALIX. 57 



Though resembling 8. humilis in general, the impression 

 made is quite different, chiefly owing to lack of the fine 

 terminals of the latter. There is also absence of comb- 

 like terminals. The veining is much weaker and earlier 

 obliterated. This, with rostrata and purpurea, are the only 

 ones in which a disposition to irregularity of the primaries 

 obtains. — Plate 3, fig. 16. 



Illustration from specimens furnished by Mr. J. Franklin 

 Collins, Providence, K. I. Rendering difficult. 



17, S. rostrata, Richardson. — Primaries few, distant, 

 crooked, not parallel, often dividing near their origin, and 

 usually sending a strong vein to each tooth, strong and 

 prominent relatively to the rest of the veining ; looping 

 irregular and wanting tipwards; intervening costals numer- 

 ous, having the same general direction. Secondaries weak, 

 scarcely stronger than the tertiaries, mostly irregular, also 

 markedly zigzag. Tertiaries weak but well defined, form- 

 ing medium-sized oblong or longish, nearly vacant (in 



mature leaf) meshes. There remains a background of 

 obscured very delicate terminals. Taking a general survey 

 of the leaf, the minute veining is seen often to assume a 



crescentic form. 



As a whole, the veining is not, as might be expected in 

 such a leaf, very uneven. Compare for example 8. tris- 

 tis. Absence of looping at tip causes it to be an exception 

 to an almost universal characteristic. — Plate 3, fig. 17. 



Illustration from specimens furnished by M. S. Bebb. 



18. S. glaucophylla, Bebb. — Primaries tend to the 

 horizontal in wide leaves, dividing well away from the mar- 

 gin, the arms forming a regular series of arches. There 

 exists besides, usually, a second, smaller set of arches 

 outside the first. Intervening costals usually but one. 

 Secondaries few, seldom regular, changing direction ab- 

 ruptly, broken or zigzag. Tertiaries prominent, consti- 

 tuting most of the veining, very irregular, forming large, 

 polygonal, defined meshes which in mature leaves do not 

 embrace any terminals, save, occasionally, a stellate point. 



12 



