REPRODUCTIVE ORGANS IN THE PRIMULACER. 111 
external agencies. When both forms, however, are artificially 
fertilized with their own pollen, we find that the long-styled unions 
are much the more fertile, exceeding the short-styled in about the 
proportion of two to one! This I have indeed found to be the 
case,in a more or less marked degree, in all the dimorphic species 
on which I have experimented, with the exception of the P. Auri- 
cula and the P. vulgaris alba, as may be seen by referring to the 
tables previously. given of those plants. Mr. Darwin notices 
(loc. cit. p. 92) this relatively decreased grade of fertility in the 
short-styled homomorphie unions, and very naturally regards it as 
a quality specially acquired for the counteraction of the greater 
facilities presented by this form than the other for self-fertilization. 
Thus, by an increased differentiation of pollen and stigma with 
respect to their mutual action, Nature renders the short-styled 
forms equally dependent with the long-styled forms on external 
agencies for the production of aught above the lowest grade of 
fertility. And thus, as Mr. Darwin has forcibly urged, one of 
the great ends of reciprocal dimorphism is more perfectly effected— 
the greatest facilities afforded for the intercrossing of individuals. 
The following table gives the results of my experiments on the 
two forms of Primula Sikkimensis :— 
Taste VIIT.— Primula Sikkimensis. 
en 
qm "i 3 5 x 4 
ETHER E 
BSE} Bur | BFE] BFE 
ao | a8 oe lon m &, 
Long-styled homomorphie union...... 24 17 248 14 
Long-styled heteromorphie union ...| 12 8 285 35 
Short-styled homomorphie union ...| 14 8 64 8 
Short-styled heteromorphie union ...| 12 10 419 42 
SUMMARY. 
The two homomorphie unions......... 35 25 312 12 
The two heteromorphie unions ...... 24 18 704 39 
In the two forms of Primula cortusoides the pistil is about 
three times as long in the one as in the other, the anthers being 
situated about the middle of the corolla-tube in the long-styled 
form, and surrounding its mouth in the short-styled form. The 
longitudinal axis of the long-styled stigmas is double that of the 
short-styled stigmas, and the stigmatic papille of the former are 
about three times longer than those of the latter. Again, the 
