Chap. VIII. STERILITY. 251 



few days perished entirely, whereas the pod impreg- 

 nated 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 confirmed 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, Rhododendron, &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 

 degree of fertility of some of the complex crosses of 

 Rhododendrons, and I am assured that many of them 

 are perfectly fertile. Mr. C. Noble, for instance, informs 

 me that he raises stocks for grafting from a hybrid 



