The Willows of Ohio. 



THE GENUS SALIX AND ITS RELATIONSHIPS. 



The willow family contains but two genera, Salix and 

 Populus. These, in most cases distinct enough in their leaves 

 are separated by the following floral differences. Populus has 

 fimbriate scales, cup shaped discs, elongated stigmas and many 

 stamens, while Salix has entire or only slightly crenate scales, 

 mostly glandular clavate discs, short stigmas and few stamens, 

 two in the majority of the species. In the polyandrous willows 

 which are treated first in the present paper, there is a distinct 

 approach from the diandrous or prevailing willow type toward 

 the poplars, most conspicuously shown in the increased number 

 of stamens but also evidenced in the disc which becomes com- 

 pound with several glands and sometimes almost forms a lop- 

 sided cup. It is, too, in the polyandrous willows and in those 

 diandrous species manifestly most closely related to them that 

 we find most of the arborescent species — a habit prevailing 

 among the poplars — while most of the willows are shrubs. 



There are recognized in all something like two hundred 

 species of willows. They are mostly natives of the north tem- 

 perate zone but are not entirely absent from the torrid and south 

 temperate zones. 



The willow may be counted one of the most successful of 

 present day plants. In few other genera, so compact and homo- 

 geneous in respect to their floral characters, is there shown so 

 great a variety of adaptations to varied conditions of life. With- 

 in this one genus may be found plants all the way from large 

 trees to dwarf herbs, affecting habitats from the fertile alluvial 

 plain to the barren mountain peak. They grow almost every- 

 where but yet there are certain limitations in their habitat. 

 Varying from hydrophytes to xerophytes, they are uniformly 

 lovers of the sun and never found to any extent in deep forests 

 or other shaded situations. In their various habitats their 

 vegetative structures undergo wide modifications to accommo- 

 date them to their environments. Some species like Salix lucid a 

 have broad thick leaves, protected from too severe conditions by 

 the hard glossy surface. In others like Salix adenophylla the 

 same protection is gained by a thick coating of wool on one or 

 both surfaces. Or a heavy coat of glaucescence may be devel- 

 oped probably to a degree at least for the same purpose. In 

 other cases the leaves are so small as to enable them to endure 

 the most severe conditions, especially when, as is often the case, 



