Ilf THE SPECIES OF PHIMtJLA, 93 



This fact is the more remarkable, because we have clearly seeu 

 that tlie short-styled form in the Cowslip in a state of nature is 

 the most productive of seed. This form bears its anthers close 

 together at the mouth of the corolla, and I observed long before 

 I had ascertained the relative fertility of the four unions, in 

 passing the proboscis of a dead Humble-bee or bristle down the 

 the corolla, that in this form the flower's own pollen was almost 

 certain to be left on its own stigma; and, as I wrote down at the 

 time, the chance of self-fertilization is much strouger in this than 

 in the other form. On this view we can at once understand the 

 good of the pollen of the short-styled form, relatively to its own 

 stigma, being the most sterile ; for tliis sterility would be the most 

 requisite to check self-fertilization, or to favour intercrossing. 

 Hence, also, it would appear that there are four grades of fertility 

 from the four possible unions in PrimziJa ; ot the two homomor- 

 phic unions, as we have just seen, one is considerably more sterile 

 than the other. In the wild state we know that the sliort-styled 

 plants are more fertile than tlic long-styled ; and we may infer as 

 almost certain, that in the wild state, when the flowers are visited 

 by insects, as is absolutely necessary for the production of seed, 

 and when pollen is freely carried from one form to the other, 

 that the unions are heteromorphic ; if so, there are two degrees of 

 fertility in the heteromorphic unions, making altogether four 

 grades of fertility. 



Two or three other points deserve a passing notice. The ques- 

 tion whether the Primrose and Cowslip (P. vulgaris and veris) are 

 distinct species or varieties has been more disputed and experi- 

 mented on than in any other plant. But as we now know tliat 

 tlie visits of insects are indispensable to the fertilization of these 

 plants, and that in all probability the heteromorphic pollen of a 

 Primrose would be prepotent on the stigma of a Cowslip over the 

 homomorphic poUeu of a Cowslip, the numerous experiments which 

 liave been made, showing that Oilips appear amongst the seed- 

 lings of Cowslips, cannot be trusted, as the parent plants do not 

 appear to have been carefully protected from insects*. I am far 

 from wishing to affii-m that pure Cowslips will not produce Ox- 



* Mr. Sidebotham (Phytologist, vol. iii. pp. 703-5) states that he protec^ed liis 

 plants from crossing ; but as he gives in detail all the precautions which he took, 

 and says nothing about artificial fertilization, we may conclude that he did not 

 fertilize his plants. As he raised very numerous seedlings, he woiJd Imvchad to 

 fertilize many flowers, if they had been really well guarded against the visits of 

 iuseetB. Hence I conclude that his results arc not wortl)y of trust. 



