DARWIN'S ALTERNATIVE EXPLANATION OF EVOLUTION. 57 



investigation is to be numbered among the chief duties of geographical 

 botany." * 



Dr. Warming found this to be the case, as the result of his ecological 

 researches in Lagoa Santa and elsewhere : "It seems to be beyond 

 doubt that the characters peculiar to growth-forms have arisen through 

 direct adaptation to the environment." f 



Professor de Vries', Professor Bateson's, and Mr. Lotsy's 

 Views. — Two new views upon the Origin of Species have been advanced 

 since Darwin's book was published : one is by Dr. H. de Vries, called 

 the " Mutation Theory " ; the other is based on the results of crossing 

 by Mr. Lotsy. Professor Bateson also appears to think that the 

 results of Mendelism may have something to do with Evolution. 



Mendelism is solely concerned with the phenomena of the results 

 from crossing or hybridizing, not with the origination of new varieties 

 without these means. It is this which raises the previous question, as 

 to their origin. M. Mendel crossed varieties of the garden pea, namely 

 those having grey and white skins ; round and wrinkled ; yellow and 

 green cotyledons ; as well as tall and short stems. The words in 

 italics are presumably the primitive characters of the wild form, 

 which, naturally, has no varieties. The other characters have been 

 acquired under cultivation. He found that the former were dominant 

 and the latter recessive. 



The primary question to ask is how did the recessive characters 

 originate ? The answer is obviously by cultivation in prepared soils, 

 as de Vries explained in his general account of the appearance of his 

 so-called " mutants," though we may be quite unable to determine 

 the individual causes ofHhe individual characters, respectively. 



In a notice of Dr. Vries' book I called attention to the fact that 

 the characters relied upon as constituting his " mutants " are not such 

 as a systematic botanist would regard as specific and scarcely varietal, 

 and that they would appear to be simply due to over-nourishment with 

 manure, causing a certain amount of degeneration, for he tells us 

 the original ground was " almost pure sand " ; on the other hand, he 

 prepared a "heavily manured" plot whereon to transplant or sow 

 them. 



Dr. de Vries explains how it is that many varieties appear in a 

 prepared soil of cultivation, unknown in the wild state. He says, 

 speaking of the external causes of the individual differences among 

 seedlings : " Moisture and manure differ on different portions of the 

 same bed in a way unavoidable even by the most careful propagator. 

 Some seeds germinate on moist and rich spots, while their neighbours 

 are impeded by local dryness or by distance from manure. Some 

 come to light on a sunny day and develop their first leaves rapidly, 

 while the following day the weather may be unfavourable and greatly 

 retard growth. The individuals seem to be due, at least in a very great 

 measure, to such apparent trifles." 



* Plant-geography upon a Physiological Basis. Preface, p. v. 

 f (Ecology of Plants, p. 373. 



