IN THE SPECIES OE PHIMULA. 91 



differing in their sexual powers and related to each other like males 

 and females. There are many hermaphrodite animals which can- 

 not fertilize themselves, but must unite with another hermaphro- 

 dite : so it is witli numerous plants ; for the pollen is often mature 

 and shed, or is mechanically protruded, before the flower's own 

 stigma is ready ; so that these hermaphrodite flowers absolutely 

 require for their sexual union the presence of another hermaphro- 

 dite. But in Primula there is this wide difference, that one indi- 

 vidual Cowslip, for instance, though it can with mechanical aid im- 

 perfectly fertilize itself, for full fertility must unite with another 

 individual ; but it cannot unite with any individual in the same 

 manner as an hermaphrodite Snail or Earth-worm can unite with 

 any other one Snail or Earth-worm ; but one form of the Cowslip, 

 to be perfectly fertile, must uuite with one of tlie other form, just 

 as a male quadruped must and can uuite only with a female. 



I have spoken of the heteromorphic union in Primula as result- 

 ing in full fertility ; and I am fully justified, for the Cowslips thus 

 fertilized actually gave rather more seed than the truly wild plants 

 — a result which may be attributed to their good treatment and 

 having grown separately. With respect to the lessened fertility 

 of the homomorphic unions, we shall appreciate its degree best by 

 the following facts. Gartner has estimated the degree of sterility 

 of the union of several distinct species *, in a manner which allows 

 of the strictest comparison with the result of the heteromorphic 

 and homomorphic unions of Prim ida. Witli P. veris, for ewerj hun- 

 dred seeds yielded by the heteromorphic unions, only sixty-four seeds 

 were yielded by an equal number of good capsules from the homo- 

 morphic unions. With P. Sinensis the proportion was nearly the 

 same — namely, as 100 to 62. Now Glartner has shown that, on the 

 calculation of Verbascum lychiitis yielding with its own pollen 

 100 seeds, it yields when fertilized by the pollen of V. Piiceiiiceum 

 ninety seeds ; by the pollen of V. nigrum, sixty-three seeds ; by 

 that of V. llattaria, sixty-two seeds. So again, Biantlius harhatus 

 fertilized by the pollen of D. superbus j-ielded eighty-one seeds, 

 and by the pollen of JD. Japonicus sixty-six seeds, relatively to 

 the 100 seeds produced by its own pollen. Thus we see— and the 

 fact is highly remarkable — that the homomorphic unions relatively 

 to the heteromorphic unions in Primula are more sterile than the 

 crosses between several distinct species relatively to the pure union 

 of those species. 



The meaning or use of the existence in Primula of the two 

 * Versuehe iiber die Bastarderzeugung, 1849, s. 216. 



