HYBRID INTERMIXTURES. 
349 
Candolle, in 1832. I have no hesitation in saying that this 
report, which seems to have been accepted as proof of what 
Gaertner had done, is utterly fallacious. He has entirely 
overlooked the difficulty, and, in many cases, the impracti- 
cability with the utmost care of excluding the natural pollen ; 
the insufficiency of a bag to shut it out, and the probability 
of its having been admitted even before the bag was placed 
over the flower. I have learned by endless disappointments 
to know, that no attempt to obtain a cross-bred plant can be 
looked upon as successful, till the seedlings raised shall have 
advanced in growth sufficiently to exhibit the type of both 
parents united in themselves ; and I consider Gaertner’s 
report of the cross-bred seeds he has obtained , to be nothing 
but a mere enumeration of the crosses he has tried to obtain ; 
and I believe some of his supposed intermixtures to be im- 
possible. The fact is, that in this country, where the passion 
for horticulture is great, and the attempts to produce hybrid 
intermixtures have been very extensive during the last 
fifteen years, not one truly bigeneric mule has been seen ; 
and, although I by no means presume to assert that such a 
production is impossible, experience shews it to be impro- 
bable ; and those, who fancy they have obtained one, must 
forgive my wishing to see it forthcoming, and to examine 
whether it is certainly of such descent as they suppose. 
Gaertner details his mode of proceeding, which is pretty 
similar to my own ; but he does not seem aware, that, in 
spite of all possible precautions, the pollen will often escape 
unobserved, and will penetrate the coverings that may be 
used. He asserts that the moist juice of the pollen combines 
with that of the stigma, to fecundate the germen, a question- 
able point, that need not here be considered. The super- 
abundant viscous juice on the stigma of Rhododendron 
appears to me to obstruct the fecundation, which I think 
takes place more readily when it subsides. Gaertner could 
not decide whether the fecundation is slow as Kolreuter 
imagined, or rapid as Hedwig asserted ; but in microsco 
pical observations the particles of pollen seemed not to be 
emptied in less than an hour and a half ; and he found that, 
when the fecundation was as he thought complete, the par- 
ticles afterwards superadded did not change form or colour ; 
but that in hybridizing applications a greater quantity of 
pollen seemed requisite, in proportion to the distance of 
affinity, and that it was repeatedly consumed ; and he 
