THE MUTATION THEORY : A CRITICISM. 



145 



Origin by Mutation " he had observed, when 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 unavoid- 

 able even by the most careful preparation. 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 increase their first leaves rapidly, while the following day 

 the weather may be unfavourable and greatly retard growth. The 

 individual differences seem to be due, at least in a very great measure, 

 to such apparent trifles." 



The mutations or " species " are named gigas, albida, ohlonga, 

 ruhrinervis, nanelJu, lata, and scintillans. 



Gigas is an exception to the rule of being weak, for while " most 

 of the new forms are weaker than the parent species (0. Lauiarckiana) 

 this is in almost every respect stronger and bigger and more heavily 

 buill " t It only arose once in the Laiiiarckiafia family and twice in 

 others. The principal difference lies in the fruits being half as long 

 and the seeds less numerous, but larger and heavier than those of the 

 parent. 



Ruhrinervis is the only one not inferior tO' 0. Lauiarckiana in pollen 

 and seed, but it has narrow and long leaves, with red ribs, red calyx 

 and fruit. It has a more vigorous habit ; but still the stems are brittle, 

 especially of the annuals, in consequence of a deficiency of bast fibres. 

 It was one of the commonest, arising sixty-six times from 0. Lamar cki- 

 ana or others. As the red colouring matter, like the red corpuscles of 

 blood, is now regarded as an oxygen-carrier, this may account for the 

 superior vigour of the mutation. 



In contrast with the two preceding types let us take albida, so 

 called from the paleness of the colours, due to impoverishment or chloro- 

 sis. The stem is very delicate and brittle. It is a slow grower, with a 

 shorter stem than that of 0. Lamar ckiana. It survived the winter with 

 difficulty, requiring great care to keep it alive. It would (Professor 

 de Vries adds) most certainly have perished in the struggle for life at 

 Hilversum, being also difficult to germinate. The leaves are narrow, 

 very uneven and pointed, but with a bluntish tip, pale-green or whitish- 

 grey, not due to hair, but to a swelling of the outer walls of the 

 epidermal cells. This " species " would seem to illustrate Darwin's 

 description : ' ' We may feel sure that any variation in the least degree 

 injurious would be rigidly destroyed." § 



I 'Suspect that any florist who might read the above diagnosis of this 

 so-called " species," 0. albida, would say that it was suffering from 

 over-manure sickness. 



It will be needless to quote so fully again; but Professor de Vries 

 admits that with the two exceptions mentioned all his species were more 

 or less delicate. Perhaps a word or two of his expressions will 

 indicate this. 



* Op. cit. p. 720. t p. 318. + p. 227. 



§ Origin of Sjjecies, &c., sixth edition, p. 63. 

 VOL. XXXVI. r 



