Chap. VIII. 
STEEILITY. 
251 
cies: the result was that the ovaries of the three 
first flowers soon ceased to grow, and after a few 
days perished entirely, whereas the pod impregnated 
by the pollen of the hybrid made vigorous growth 
and rapid progress to maturity, and bore good seed, 
which vegetated freely.” In a letter to me, in 1839, 
Mr. Herbert told me that he had then tried the 
experiment during five years, and he continued to try 
it during several subsequent years, and always with the 
same result. This result has, also, been conflrmed by 
other observers in the case of Hippeastrum with its 
sub-genera, and in the case of some other genera, as 
Lobelia, Passiflora and Verbascum. Although the plants 
in these experiments appeared perfectly healthy, and 
although both the ovules and pollen of the same 
flower were perfectly good with respect to other species, 
yet as they were functionally imperfect in their mutual 
self-action, we must infer that the plants were in an 
unnatural state. Nevertheless these facts show on what 
slight and mysterious causes the lesser or greater fer¬ 
tility of species when crossed, in comparison with the 
same species when self-fertilised, sometimes depends. 
The practical experiments of horticulturists, though 
not made with scientific precision, deserve some 
notice. It is notorious in how complicated a manner 
the species of Pelargonium, Fuchsia, Calceolaria, Pe¬ 
tunia, Ehododendron, &c., have been crossed, yet many 
of these hybrids seed freely. For instance, Herbert 
asserts that a hybrid from Calceolaria integrifolia 
and plantaginea, species most widely dissimilar in 
general habit, ^‘reproduced itself as perfectly as if 
it had been a natural species from the mountains of 
Chile.” I have taken some pains to ascertain the 
degTee of fertility of some of the complex crosses of 
Ehododendrons, and I am assured that many of them 
