36 



ROYAL HORTICULTURAL SOCIETY. 



X. On Variability in the Pear-tree, the result of Experiments made 

 at the Museum of Natural History from 1853 to 1862. By 

 M. J. Decaisne* 



The almost unlimited and still increasing number of varieties in 

 fruit-trees, pulse, and all economical vegetables in general, is a 

 phenomenon to which science has hitherto paid little attention. 

 There is the greater reason to be astonished at this, since it has 

 been remarked even by persons most unaccustomed to the study 

 of plants, and since, from the earliest times, it has been an object 

 of importance on the part of cultivators. 



Writers of antiquity — Theophrastus, Pliny, Columella, and 

 others, like those who have succeeded them in ages nearer to the 

 present, the brothers Bauhin, Ch. Estienne, T. Dalechamp, &c. — 

 have described a tolerably large number of these varieties, espe- 

 cially in fruit-trees, where they were the most apparent ; but one 

 would in vain search for their origin in their writings : though 

 they let us vaguely suppose that they are, or may be, the produce 

 of cultivation, none of them say positively that any particular 

 new variety sprang from any other ; none of them explains why 

 they have gone on multiplying from age to age. Are these new 

 forms, then, as has been recently alleged, real species, which re- 

 mained unrecognized up to the time when it was proposed to 

 submit them to cultivation ? or are they only modifications of 

 long-known species, endowed with the faculty of assuming differ- 

 ent habits, according to circumstance of place and climate ? It 

 may seem astonishing that such a question should be brought be- 

 fore the Academy, so natural does it seem to believe that species 

 are subject to variation; but we shall see presently that this 

 question is not one of those which we ought to leave without ex- 

 amination : if it is important as regards practical agriculture, it is 

 not less so as regards science itself. 



Two schools, or I should rather say, two different hypotheses 

 divide botanists at the present moment. The most ancient, which 

 I may call that of the Linnsean school, admits the variability of 

 species within limits, which, to say the truth, it is not always easy 

 to define; hence those large, polymorphous, and sometimes vaguely- 

 defined species, though in general easily characterized by a short 

 specific character. The other school, which is more especially 

 modern, and which, I believe, may be called the school of immuta- 



* Translated from ' Annales des Sciences Naturelles,' 4 serie, vol. xx. p. 188 

 (1804). 



