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REVISION OF THE BRITISH WILLOWS. 383 



of Salix, the continental salicclogists have described more forms 

 of S. aurita than British botanists have done. 



Thus Andersson specifies three, and Wimmer four, principal 

 modifications ; but as these are so connected by other intermediate 

 forms that it is often impossible to say to which a specimen should 

 be referred, it seems unnecessary to mention them by name. 



S. aurita, like its allies, is subject to a great range of variation. 

 At the same time it can usually be recognized without much 

 difficulty, not so much by any one characteristic as by a combi- 

 nation of them and its general appearance. Its closest affinity 

 is with S. cinerea, and, so far as dried leaf-specimens go, it is 

 sometimes not easy to determine to which species they belong, 

 since certain features of the twigs and buds, described as charac- 

 tenstic of the species, will, in practice, be found not quite reliable. 

 Thus the year-old twigs, which ought to be glabrous, are not 

 unfrequently more or less slightly pubescent in S. aurita, and 

 glabrous when they ought to be tomentose in S. cinerea ; and the 

 buds are glabrous or pubescent, though described variously as 

 one or the other. 



From this close relationship it follows that the hybrids between 

 *. aurita and S. cinerea, when not exactly intermediate but more 

 related to one or other of the parents, can only be distinguished 

 with great difficulty. 



XSalix lutescens, A. Kern. (S. cinerea xS. aurita.) 



Wimmer remarks that the hybrid forms— which he calls 8. 



writa-cinerea— between S. cinerea and S. aurita are most difficult 



ma ^ e ou t> since the differences between the species themselves 



are not easily expressed in written notes, but that, nevertheless, 



such hybrids seem to be commoner than has been thought. If 



e stu <lent, however, has familiarized himself with the two 



species in question, so as to understand, in some degree at least, 



e range of their variation, the difficulty of recognizing the 



J nd torms is not insurmountable when they occupy a more or 



le88 mtennediate position. 



as is 



Wh 







ver y frequently the case in such plants, greater affinity with 



parent than the other, absolute certainty becomes well-nigh 

 ^possible. 



I . * P 01I *t8 of distinction between S. cinerea and S. aurita to be 

 j Kept in mind are as follows : — twigs, in aurita more slender 







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