200 MR. J. SCOTT ON THE STERILITY AND HYBRIDIZATION 
eight flowers of the P. alata No.1. The ovaries of four of these 
swelled for some time, but ultimately one of them shanked off, 
while the other three reached perfection and yielded in all 674 
seeds, of which 560 appeared to be good. By the converse ex- 
periment the results were very different ; thus, four flowers of the 
P. alata No. 2 were impregnated with pollen of the P. alata 
No.1, but each of these dropped off, without affording the 
slightest symptoms of fertilization. Again, on the P. alata No. 1 
I fertilized six flowers with pollen of P. alata No. 3; but though 
the ovaries of two of these set, and continued swelling for some 
time, they ultimately dropped prematurely and did not yield any 
good seed. I also had in this case the converse experiment tried 
for me, and from four flowers on the P. alata No. 3 fertilized 
with pollen of the P. alata No. 1, one ovary was induced to set; 
but, as in the converse case, this did not continue to swell. See- 
ing, however, that in either of these cases so few flowers were 
experimented upon, we may, I think, with justice be permitted to 
infer from the results that more extended experiments would 
show them capable of reciprocally fertilizing each other. I dis- 
sected some flowers of these three plants of P. alata which had 
been treated with each other's pollen, and found the stigmas 
abundantly penetrated by pollen-tubes. This fact, together with 
the swelling of the ovaries, shows a much higher degree of reci- 
procal susceptibility to each other's pollen than exists (as we 
shall presently see) in any one of these plants when fertilized 
with pollen from the same individual plant. 
The following results of experiments on the P. alata No. 1 as 
female with pollen of other species may also be worthy of notice 
in this place, from the fact that similar or reciprocal unions have 
been effected by different experimenters; and, further, that in 
at least one of the cases to be mentioned—that of P. alata 
No. 1 by pollen of P racemosa—1 have found, as above shown, 
that fertile unions may be readily effected, while the others, 
either directly or indirectly, dovetail themselves into each other 
by curious and complex fertile conjunctions, as will be found by & 
careful study of my experiments as detailed. First, I placed 
pollen of P. racemosa on the stigmas of ten flowers of the P. alata 
No. 1, but these all dropped off, without so much as the ovary of 
one swelling. Secondly, sixteen flowers on the P. alata No. 1 
were impregnated with pollen from the plants Nos. 1 & 2 of 
P. eerulea, but in these cases also every ovary aborted. Thirdly, 
in the case of P. alata No. 1 by pollen of P. edulis the results 
