126 BULBILS AND GEMMJE. 



indeed, {Lunularia) perpetuates itself in this country by gemmee 

 alone, the spore-bearing form never having been found.* On 

 the other hand Pellia epiphylla, common on damp banks and by 

 water-courses, bears spores to the entire exclusion of gemmee.f 

 Incidentally, the writer may mention that his personal observa- 

 tions on the common Marchantia, grown in stove- houses, show 

 that a high and humid atmosphere favours the male form, which 

 under these circumstances is always in excess of the female. 

 This is an interesting supplement to Professor Henslow's 

 assertion — "A relatively high temperature favours the,... 

 andrcecium, while a comparatively lower one the gynaecium."J 



This, then, is the evidence. Like the arms of an octopus, 

 the subject stretches away in other directions, and many sub- 

 sidiary studies are involved. Indeed it will be clearly seen that 

 an equally great problem lies behind the whole. It is easy, and 

 to a certain degree interesting, to say that, defeated in her 

 purpose of ripening seed and spores, Nature has taken another 

 and shorter cut to the same end by allowing the reproductive 

 energy to express itself in the form of bulbils and gemmae ; but 

 the inquisitive student asks for more. To him it is of supreme 

 import to know how and why nature has been frustrated in her 

 purpose to develop seed ; and on other points he raises equally 

 pertinent questions. In a great measure these have been 

 answered elsewhere, and by competent writers, hence it would 

 be without the province of this paper to go into details. The 

 works of Mtiller, Darwin, Dr. Masters, and Henslow are lucid 

 expositions of the action of environment upon irritable 

 protoplasm. These writers have made it abundantly clear that 

 temperature, soil, and insects are powerful agencies in modifying 

 the structures and transmitting the form and colour of flowers, 

 exacting a change here and another there, and intensifying 

 the whole through succeeding generations until what at first 

 seemed trivial and fitful aberrations from the type, culminate in 

 distinct and fixed variations. 



* A course of practical instruction in Botany, by F. O. Bower, D.Sc, P.L.S. 

 1891, p. 362. 



X The origin of Floral Structures, p. 237. 



