IN THE SPECIES OF PRIMULA, 93 
This fact is the more remarkable, because we have clearly seen 
that the 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 stronger 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; forthis 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 Primula; of 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 short-styled 
plants are more fertile than the 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 heteromorphie ; if so, there are two degrees of 
fertility in the heteromorphie 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 
distinet species or varieties has been more disputed and experi- . 
, nented on than in any other plant. But as we now know that 
the visits of insects are indispensable to the fertilization of these 
plants, and that in all probability the heteromorphie pollen of a 
Primrose would be prepotent on the stigma of a Cowslip over the 
homomorphic pollen of a Cowslip, the numerous experiments which 
have been made, showing that Oxlips 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 affirm that pure Cowslips will not produce Ox- 
* Mr. Sidebotham (Phytologist, vol. iii. pp. 703-5) states that he protected his 
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 would have had to 
fertilize many flowers, if they had been really well guarded against the visits of 
Insects, Hence I conclude that his results are not worthy of trust. 
