1897] ORIGIN OF SPECIES AMONG PLANTS 167 



are theoretically assumed to be, constant." One or more of these 

 characters may be found on another species, which in a similar 

 manner is known by its collection of constant characters. 



What may have been their origin, and how the survival and 

 maintenance of any superficial characters of a plant have been 

 secured, are philosophical questions with which the systematist has 

 no concern at all. 



Useless Characters. — Before showing that the hypothesis ef 

 natural selection is superfluous in the origination of varietal charac- 

 ters, let us turn to the descriptions of plants given in some standard 

 work, say, Sir J. D. Hooker's " Students' Flora of the British Isles." 

 It will be found that many characters are taken as specific or 

 generic which cannot, with any show of reason, be regarded as 

 specifically useful ; such as the numerical excess or deficiency in 

 the number of parts in the floral whorls ; e.g., Gcntiana campestris 

 is described as having the calyx "four-partite"; while in G-. amarella, 

 it is " five-lobed " ; but fours, fives and sixes may be often found on 

 one and the same plant, as in a corymb of elder flowers, due to an 

 accidental deficiency or excess of nutriment, respectively ; and no 

 vital importance can be attributed to the trivial specific distinc- 

 tion between " partite " and " lobed." Such illustrations of quite 

 unimportant characters regarded as specific can be multiplied to 

 any extent ; but they are some of the very characters which 

 Darwin admits are not due to natural selection. He says : 

 — " We thus see that with plants many morphological changes 

 may be attributed to the laws of growth and interaction of parts, 

 independently of natural selection." l They are, in fact, simply 

 the inevitable results of a response to environmental conditions, using 

 the term in the broadest sense. 



With regard to such indifferent characters being hereditary, 

 Darwin first says that he " felt great difficulty in understanding the 

 origin or formation of parts of little importance ; almost as great, 

 though of a different kind, as in the case of the most perfect and 

 complex organs," 2 and he devotes a section to a theoretical 

 interpretation of them. Indeed he, on several occasions, recognises 

 the existence of useless characters ; e.g., he says, " I am inclined to 

 suspect that we see, at least in some of the polymorphic genera, 

 variations which are of no service or disservice to the species ; and, 

 consequently, have not been seized on and rendered definite by 

 natural selection." 3 In this passage the word " disservice " almost 

 seems as if he had a suspicion that " injurious " characters might 

 sometimes be present, though he elsewhere says : — " Any actually 

 injurious deviations in their structure would, of course, have been 



1 " Origin of Species," 6th ert., p. 175 ; see also p. 367. 



2 " Origin, etc.," p. 156. ■"' " Origin, etc.," p. 35. 



