Transactions. 95 



2. Nithsdale Willoivs, by Mr James Fingland, Thornhill. 



By the publication in November, 1890, of a " Revision of 

 British Willows," by Dr F. Buchanan Wliite, in tlie Journal of 

 the Linnean Society, a fresh impetus has been given to the study 

 of th's difficult family of plants. As Dr White's " Revision " 

 introduces a new system of classification and overturns, to a 

 considerable extent, previous methods of classifying our willows, 

 it is perhaps not out of place here to ascertain at least the out- 

 lines of the arrangement he adopts, and what grounds he has for 

 making the revision. 



Dr White, in his introductory part, shows how botanical 

 opinion has undergone many changes in estimating the number 

 of different willow species. The great variety of forms which 

 occur in this family, and the extreme variability which charac- 

 terise even the more stable forms, or those forms which are 

 undoubtedly specific, have been a source of great difficulty to 

 those botanists who have sought to define and classify them. 

 When that eminent botanist, Sir J. E. Smith, in his " English 

 Flora," published in 1828, tells his readers that he had laboured 

 for 30 years at the task of specific definition, some idea may be 

 formed of the extent of the undertaking. Sir J. E. Smith, in 

 his work referred to, defined 64 species of willows. Since then the 

 number of estimated species has fluctuated with the opinions of suc- 

 ceeding botanical authors until we reach the last (8th) edition of 

 the " London Catalogue of Plants," which is understood to 

 represent current botanical science. There are 96 forms of 

 British willows given in this catalogue, 31 of which have specific 

 rank, the remaining number being placed as varieties or sub- 

 species. None of tliese arrangements have hitherto met the 

 necessities of the case, nor have the definitions been comprehen- 

 sive enough to embrace all the gradations of form which are 

 found to exist. 



Dr White bases his classification on a recognition of the cir- 

 cumstance of hybridization being an active element in causing 

 the great variability in willows. The early salicologists, it seems, 

 were unwilling to admit this. It has, however, been found that 

 binary and ternary hybrids occur spontaneously. This, too, has 

 been proved by experiment on the part of a continental botanist. 

 Max Wichura, who has also found that by cross-fertilising these 



