







396 



DR. F. BUCHANAN WHITE S 





moreover, they are occasionally not in accordance with the authors 



own diagnoses. 



In their extreme forms Salix phylicifolia and S. nigricans can 

 be separated without any difficulty, but a by no means incon- 

 siderable number of examples exhibit such a combination of the 

 characteristics of each, that it is impossible to determine under 

 which name they should be placed. It may be the case that these 

 perplexiug forms are, as gome authors suppose, hybrids between 

 two distinct species ; but, in view of the polymorphic nature of 

 both S. phylicifolia and 8. nigricans, it seems more probable that 

 they are only intermediates which connect the extremes of one 

 most variable willow. Adopting this view, I combine them under 

 the name of 8. phylicifolia, L., which seems to have originally 

 included both. 



9. Salix phylicifolia, L. 



Whilst adopting the Linnean name for the series of European 

 species which have been made out of 8. phylicifolia, two subspecies 

 or major varieties, namely a. S. phylicifolia, L., Auct., and (Z- »• 

 nigricans, Sm M should be distinguished. 



The chief distinctions between phylicifolia and nigricans lie in 

 the leaves and twigs. In S. phylicifolia the leaves are thicker and 

 of a firmer texture, of a brighter and more shining green on the 

 upper surface and often more glaucous below ; whilst in nigricans 

 they are thinner, less compact in substance, of a duller green and 

 less shining above, and usually less brightly glaucous below- 

 both forms the underside may be green. 8. nigricans has also a 

 greater tendency to turn black in drying, but this is by no means 

 invariable, and is of no real value as a characteristic, since some 

 nigricans forms do not change colour and others appear to do so 

 always. 



The leaves of S. phylicifolia are not only less pubescent (some- 

 times, indeed, perfectly glabrous), with the pubescence quite or 

 nearly disappearing at an earlier stage of their growth, but the 

 hairs are usually— not always, perhaps — of a different character 

 from those of nigricans. In S. phylicifolia the hairs are rather 

 stouter, shorter, and straighter, somewhat shining, and, though 

 mostly white in colour, have a mixture of bright red-brown ones. 

 In nigricans the hairs, which are more numerous and sometimes 



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