THE WILLOWS OF OHIO. 301 



of its leaves contrasting strongly with the rich green of the upper 

 surface. In some hybrids, however, most noteworthily Salix 

 Candida x. 5. petiolaris the resemblance is so close as to make it 

 all but impossible to separate the two. But such hybrids usually 

 have a distant scolloped serration derived from 5. petiolaris 

 which is different from any form of 5. humilis. At flowering 

 time there will be no difficulty in separating them. 



Salix humilis var. tristis (Ait.) Dwarf Gray Willow. 



A depauperate form of 5. humilis with which it is connected 

 by many intermediates. It may be described as smaller and 

 hairier throughout. It is quite low (to 6 dm.) with smaller 

 leaves (to 5 cm. long) more strongly gray tomentose, and catkins 

 sometimes scarcely 5 mm. long. This can hardly be regarded as 

 a distinct species. There is not a single constant character by 

 which the two differ and what differences there are, are such as 

 would be likely to be caused by differences in environment. 

 Such forms should be considered as varieties rather than as 

 species. 



SERICEAE. 



Swamp shrubs, leaves narrowly elliptic-lanceolate, com- 

 monly tapering to both ends, serrate with blunt cartilaginous 

 teeth to entire, glabrous to glaucous, sericeate below when young, 

 generally blackening in drying. Aments born before the "leaves, 

 sessile or short peduncled, scales darkened at the tip, pilose, 

 capsules pedicelled, silvery sericeate at least when young. 



Key. 



From leaves. 



Leaves dull above, silvery silky beneath at least until very 



old, scarcely glaucous. 5. sericea. 



Leaves shining above, glabrous on both sides except when 



young, pubescence on young leaves mostly ferruginous, 



quite glaucous below. 5. petiolaris. 



From flowers. 



Fruiting catkins dense, sessile, capsule ovoid-conic, obtuse, 



short pedicelled, sericeate even when ripe, hardly 4 mm. 



long. 5. sericea' 



Fruiting caktins, looser, short peduncled, capsule becoming 



cvlindric conic, acutish, long pedicelled, nearly glabrous 



when mature, more than -1 mm. long. S. petiolaris. 



Plate XI. Salix sericea. 



Typical leaves flowers and fruit; natural size; ripe capsule drawn in 

 with camera lucida, enlarged five times. 



