48 AUTOBIOGRAPHY. [ch. ii. 



of Linum flavum, and had at first thought that it was 

 merely a case of unmeaning variability. But on examining 

 the common species of Primula, I found that the two forms 

 were much too regular and constant to be thus viewed. I 

 therefore became almost convinced that the common cowslip 

 and primrose were on the high-road to become dioecious ; 

 that the short pistil in the one form, and the short stamens 

 in the other form were tending towards abortion. The 

 plants were therefore subjected under this point of view to 

 trial ; but as soon as the flowers with short pistils fertilised 

 with pollen from the short stamens, were found to yield 

 more seeds than any other of the four possible unions, the 

 abortion-theory was knocked on the head. After some ad- 

 ditional experiment, it became evident that the two forms, 

 though both were perfect hermaphrodites, bore almost the 

 same relation to one another as do the two sexes of an ordi- 

 nary animal. With Lythrum we have the still more won- 

 derful case of three forms standing in a similar relation to 

 one another. I afterwards found that the offspring from 

 the union of two plants belonging to the same forms pre- 

 sented a close and curious analogy with hybrids from the 

 union of two distinct species. 



In the autumn of 1864 I finished a long paper on Climb- 

 ing Plants, and sent it to the Linnean Society. The writing 

 of this paper cost me four months; but I was so unwell 

 when I received the proof-sheets, that I was forced to leave 

 them very badly and often obscurely expressed. The paper 

 was little noticed, but when in 1875 it was corrected and 

 published as a separate book it sold well. I was led to take 

 up this subject by reading a short paper by Asa Gray, pub- 

 lished in 1858. He sent me seeds, and on raising some 

 plants I was so much fascinated and perplexed by the revolv- 

 ing movements of the tendrils and stems, which movements 

 are really very simple, though appearing at first sight very 

 complex, that I procured various other kinds of climbing 

 plants, and studied the whole subject. I was all the more 

 attracted to it, from not being at all satisfied with the ex- 

 planation which Henslow gave us in his lectures, about 

 twining plants, namely, that they had a natural tendency to 

 grow up in a spire. This explanation proved quite erro- 

 neous. Some of the adaptations displayed by climbing 

 plants are as beautiful as those of Orchids for ensuring 

 cross-fertilisation. 



My Variation of Animals and Plants under Domestica- 



