IS THE SPECIES OE PMMfLA. 81 



slip, as does the length of the stamens. But it is remarkably that 

 the pollen-grains of both forms, wet and dry, presented no differ- 

 ence in diameter ; they vary somewhat in size, as do the pollen- 

 grains of all the species, but in both forms the average diameter 

 was ratlier above -^^%g of an inch. There is one remarkable dit- 

 ference in the two forms of this species, namely (as we shall pre- 

 sently more fully see), that the short -styled plants, if insects be 

 excluded and there be no artifleial fertdization, are quite sterile, 

 whereas the long-styled produce a moderate quantity of seed. But 

 when both forms are properly fertilized, the short-styled flowers 

 (as with Cowslips) yield more seed than the long-styled. In a lot 

 of seedlings which I raised, there were thirteen long-styled and 

 seven short-styled plants. 



Of Primula ciliata a long-styled specimen, and of P. ciliata, var. 

 pwrpurata, a short- styled specimen, were sent me from Kew by 

 Prof. Oliver. This case, however, is hardly worth giving, as the 

 \axietj purpurata is said* to be a hybrid between this species and 

 P. auricula ; and the height of the stamens in the one form does not 

 correspond with tlio height of the stigma in the other, as they 

 would have done had they been the same sjjecies. There was, 

 however, the usual difference in the roughness of the stigmas in 

 the two forms, and the pollen-grains, distended in water, measured 

 gg^ and ^ of an inch in diameter. Single trusses were sent me 

 of P. denticulata and P. Piedmontana whichi were long-styled, and 

 of P. maryinata and nivalis which were shorfc-styled ; and the 

 general character of the organs leaves hardly any doubt on my 

 mind that these species are dimorphic. In a single flower of P. 

 Sibirica, however, which was sent me from Kew, the stigma reached 

 up to the base of tlie anthers ; so that this species is not dimorphic, 

 or not dimorphic as far as the length of the pistil and stamens are 

 concerned, unless indeed this single specimen was anomalous, like 

 that mentioned of P. auricula. 



We thus see that the existence of two forms is very general, if 

 not universal, in the genus Primula. The simple fact of the 

 pollen-grains differing in size and outline, and the stigma, in shape 

 and rouglmess, in two sets of individuals of the same species, is 

 curious. But what, it may be asked, is the meaning of these 

 several differences? The question seems worthy of careful inves- 

 tigation, for, as far as I know, the use or meaning of dimorphism 

 in plants has never been explained ; hence, I w ill give my obser- 



* Sweet's ' JHowcr Garden,' rol. v. (ab. 123. 

 LINK. mOC DOTAiyY. VOL. VI. (■ 



