TRANSMUTATION OF PLANTS. 



250 



nition, do exist throughout nature. It is too convenient a 

 term to be dispensed with, even as an assumption ; only care 

 should be taken that we do not accept the abstract term for 

 the fact Mr. Westwood, speaking of insects, says, " In 

 very extensive genera, the distinctions of species are so 

 minute, that it requires the most practiced eye to separate 

 them ; and, indeed, there are some groups, the species of 

 which are so intricately blended together, that no two en- 

 tomologists are agreed as to their distinctness." Accord- 

 ing to Mr. Haldeman, author of a learned work on the 

 fresh-water mollusks of America, "There are distinct 

 species in that class — among the Unionidae, for example 

 [and this is a remark applicable to other departments of 

 the animal kingdom,] actually differing less from each 

 other than the known varieties of certain variable species 

 which a Lamarkian might suppose to be of so recent an 

 origin as not to have yet become settled in the possession 

 of their proper diagnostic characters. Indeed, notwith- 

 standing the assumption to the contrary, by authors who 

 have little practical acquaintance with the details of natu- 

 ral history, the proper discrimination between species 

 and variety, is one of the greatest difficulties which the 

 naturalist has to encounter ; and he who is successful in 

 this department is entitled to a rank which comparatively 

 few can attain. "f 



Of the extent to which modifications may be carried 

 by palpable external conditions, I may now supply a few 

 illustrations. It is well known that fungi and lichens 

 attain to very different appearances in different situations, 

 in conformity with different conditions. Fries, we are 

 told, " asserts that out of the different states of one spe- 

 cies (telephora sulphurea) more than eight distinct gen- 

 era had been constructed by different authors. It would 

 seem, then, that the absolute number of species among 

 the fungi is not nearly so great as has been usually sup- 

 posed, and that the kind produced by a decomposing 

 infusion, or a bed of decaying solid matter, will depend 

 as much upon the influence of the material employed 

 as upon the germ itself which is the subject of it.% 



Among the questions proposed by the Academy of Sci 

 ences at Haarlem, in 1839, was one upon the followir^ 



* Linnsean Transactions, xv., 482. 

 f Boston Journal of Natural History 

 i Carpenter's Physiology, p ^2 



