MR. J. SCOTT ON PASSIFLORA, DISEMMA, AND TACSONIA. 197 
Notes on the Sterility and Hybridization of certain Speeies of 
Passiflora, Disemma, and Tacsonia. By Mr. Jons Scott. 
Communicated by C. Darwın, Esq., F.R.S. & LS. 
[Read June 16, 1864.] 
In the Royal Botanic Gardens of Edinburgh, plants of the Passi- 
flora racemosa, cerulea, and alata have been grown for a number of 
years; yet Mr. M‘Nab has informed me that, though annually 
yielding a profusion of blooms, he has never known them to pro- 
duce a single seed. That this sterility originates in the impotent 
action of the male and female sexual elements on each other, and 
not merely, as might be suspected, from the pollen not reaching 
the stigmas, I have fully satisfied myself by continued experiments 
throughout the flowering seasons of 1861 and 1862. During both 
seasons I fertilized on each plant of the above-named species a vast 
number of flowers with their own pollen, but not one of them 
produced a single seed. I may also state,as further confirmatory 
of the functional impotence of at least P. racemosa and P. alata, 
that similar experiments have been made by one or two other 
young men in the Botanic Gardens with the same result. In 
one or two instances, indeed, in our experiments on P. racemosa 
fruits were produced; but these proved destitute of seed, the 
walls of the ovaries being alone developed. 
A similar inveterate self-sterility in plants of the above species 
has been frequently noticed; and in one or two instances it has 
been found (but I have no books at hand for reference) that, though 
thus utterly impregnable to their own pollen, they are nevertheless 
susceptible to fertilization by that of certain allied species, while 
the potency of their own pollen has been proved by its effectively 
fertilizing other species. Accordingly, in 1863, I again instituted 
a series of experiments on these plants of the Passiflora racemosa, 
cerulea, and alata, in the Botanic Gardens of Edinburgh, by way 
of eliciting the nature of their sterility, and proving whether or 
not they were susceptible to reciprocal fertilization with other 
individuals of the same, or of allied species. The results of these 
experiments are so curious, that I think it will be worth while 
to communicate them to the Society in detail; they are as 
follows*. 
* I am greatly indebted to Mr. J. B. Sterling for giving me pollen from a 
plant of the P. alata in the nurseries of the Messrs. Lawson and Sons, Edin- 
burgh; and for trying experiments on this plant with its own pollen and with 
that of other species. I have also to express my thanks to a gentleman at 
