have received two authentic accounts of _P.
quadrangularis_, which never produced fruit with its own pollen, but
would do so freely when fertilised in one case with the pollen of _P.
coerulea_, and in another case with that of _P. edulis_. So again, with
respect to _P. laurifolia_, a cultivator of much experience has
recently remarked[315] that the flowers "must be fertilised with the
pollen of _P. coerulea_, or of some other common kind, as their own
pollen will not fertilise them." But the fullest details on this
subject have been given by Mr. Scott:[316] plants of _Passiflora
racemosa_, _coerulea_, and _alata_ flowered profusely during many years
in the Botanic Gardens of Edinburgh, and, though repeatedly fertilised
by Mr. Scott and by others with their own pollen, never produced any
seed; yet this occurred at once with all three species when they were
crossed together in various ways. But in the case of _P. coerulea_,
three plants, two of which grew in the Botanic Gardens, were all
rendered fertile, merely by impregnating the one with pollen of the
other. The same result was attained in the same manner with _P. alata_,
but only with one plant out of three. As so many self-sterile species
have been mentioned, it may be stated that in the case of _P.
gracilis_, which is an annual, the flowers are nearly as fertile with
their own pollen as with that from a distinct plant; thus sixteen
flowers {138} spontaneously self-fertilised produced fruit, each
containing on an average 21.3 seed, whilst fruit from fourteen crossed
flowers contained 24.1 seed.

Returning to _P. alata_, I have received (1866) some interesting
details from Mr. Robinson Munro. Three plants, including one in
England, have already been mentioned which were inveterately
self-sterile, and Mr. Munro informs me of several others which, after
repeated trials during many years, have been found in the same
predicament. At some other places, however, this species fruits readily
when fertilised with its own pollen. At Taymouth Castle there is a
plant which was formerly grafted by Mr. Donaldson on a distinct
species, name unknown, and ever since the operation it has produced
fruit in abundance by its own pollen; so that this small and unnatural
change in the state of this plant has restored its self-fertility! Some
of the seedl