REPRODUCTIVE ORGANS IN THE PRIMULACEX. 105 
the homomorphic unions; and so we find it to be in all the unions 
of the common Primrose with the white variety given in Table V. 
Though there are certainly great irregularities as to the grade of 
fertility of the different unions, we have still extending through 
all, the important parallelism that the heteromorphic unions in 
every case exceed the homomorphic unions. We thus see (and the 
fact is most interesting) that though the Polyanthus and White 
Primrose have been greatly differentiated with respect to their 
sexual relations with their common parent, P. vulgaris, it is yet 
insufficient to derange the operations of the laws of dimorphism 
by rendering the heteromorphie and homomorphie unions indif- 
ferently the more fertile. By comparing the relative fertility of 
the different cross-unions of these forms, however, we are forcibly 
impressed with the occasional unimportance of structural differ- 
ences on the functional correlations of distinct forms. Who, for 
example, in absence of proof, would have suspected that unions 
between the Polyanthus and the common yellow Primrose would 
afford a higher grade of fertility than those of the latter (the 
common Primrose) with the red and white Primroses, which, so 
far as can be discerned, differ from each other in colour alone ? 
Nevertheless such is the case: we have shown that the red 
Primrose will not unite with either the yellow or white Primrose, 
and that a very imperfect fertility results from the unions of the 
two latter forms,—the united heteromorphic unions of the common 
Primrose by pollen of the Polyanthus producing more seed than 
the similar unions of the ‚former by pollen of the white Primrose, 
in about the proportion of twenty-seven to eighteen seeds per 
capsule, or as three to two! 
I have previously stated that individuals of truly dimorphic 
species occasionally appear with stamens and pistils of an equal 
length ; and also gave an instance of the occurrence of such an in- 
dividual in P. Awricula, with the results of experiments illustra- 
ting the effects of such a structure on the functions of reproduc- 
tion. I will now give an additional and much more remarkable 
illustration of this from my observations on P. veris, Amongst 
a number of seedling Cowslips I observed an individual with 
stamens and pistils of an equal length, both reaching the mouth 
of the corolla-tube. On examination, however, I found it to 
differ importantly from the non-dimorphie individual of P, Auri- 
cula. The pollen-grains were as large as, or even larger than, 
those of normal short-styled plants: the stigma globular, and rough 
with papille,—in fact, a perfect fac-simile of that characteristic of 
