IN THE SPECIES OF PRIMULA. 81 
slip, as does the length of the stamens. But it is remarkable 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 rather above 419. of an inch. There is one remarkable dif- 
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 artificial fertilization, 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. 
purpurata, a short-styled specimen, were sent me from Kew by 
Prof. Oliver. This case, however, is hardly worth giving, as the 
variety 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 the height of the stigma in the other, as they 
would have done had they been the same species. There was, 
however, the usual difference in the roughness of the stigmas in 
the two forms, and the pollen-grains, distended in water, measured 
am and $œ of an inch in diameter. Single trusses were sent me 
of P. denticulata and P. Piedmontana which were long-styled, and 
of P. marginata and nivalis which were short-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 the 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 i in size and outline, and the stigma, in shape 
and roughness, 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 dimorphisin 
in plants has never been explained; hence, I will give my obser- 
* Sweet's ‘ Flower Garden,’ vol. v. tab. 123. 
LINN. PROC —BOTANY, VOL. VI. G 
