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."! 



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 indifferent 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^ 



* Linnaean Transactions, xv., 482. 

 f Boston Journal of Natural History 

 i Carpenter's Physiology, p. 62 



