202 MR. J. SCOTT ON THE STERILITY AND HYBRIDIZATION 
from external appearance, were good. Again, three flowers on 
the D. coccinea fertilized by own pollen produced three fine fruits 
and 586 good seeds. On the stigmas of six other flowers of 
JD. coccinea Y placed pollen of the P. alata No. 1, and got two 
ovaries to set, but only one continued swelling, and yielded in all 
74 seeds, of which only 12 were plump and apparently good. 
5. In the Royal Botanic Gardens of Edinburgh there are, be- 
sides these perfectly self-sterile individuals already noticed, plants 
of two other species of Passiflora worthy of a passing notice from 
a similar inveterate self-sterility. These are the P. holosericca 
and P. manora. First, for their reciprocal fertilization, I placed 
pollen of P. manora upon the stigmas of ten flowers of the P. ho- 
losericea; the ovaries of seven of these set, and ultimately pro- 
duced, in so far as could be judged from the plump, round, palish- 
yellow ovaries, perfect fruits. On dissecting these, however, I 
was disappointed to find that the walls of the ovary had alone 
been developed, and that they were all destitute of aught but 
the veriest rudiments of seeds. I have frequently repeated 
this experiment, and in every instance I found that the develop- 
ment of the ovaria of the P. holosericea may thus be readily 
effected by the pollen of the P. manora, whereas it is utterly 
impotent in exciting the slightest development of the seeds. I 
likewise tried the converse experiment, and applied pollen of 
P. holosericea to the stigmas of ten flowers of the P. manora; of 
these only one ovary set, but this soon shanked off. Though I 
have frequently repeated this experiment, I have not again got a 
single ovary to set. Again, with respect to the fertilization of 
these species with own pollen, I may state generally that though 
I have thus fertilized a vast number of flowers on both plants in 
the successive flowering seasons of 1862 and 1863, yet in no in- 
stance did a single fruit set. I also examined the stigmas of 
several flowers on both plants after the application of own pollen, 
and invariably found that the stigmas had failed to excite the 
development of a single pollen-tube. On the other hand, pollen 
of the P. manora readily protrudes its tubes when placed on the 
stigmas of P. holosericea, though, as we have shown, it utterly 
fails in effecting the vitalization or even development of the 
seeds. In the converse experiments I also examined the stigmas 
of P. manora after being covered with the pollen of P. holosericea, 
and in several instances found the pollen-tubes protruding and 
penetrating the stigmas, though, as we have seen, they fail to 
effect a fertilizing influence. 
