CHAP. IX. DEGREES OF STERILITY. 223 



This cas of the Crinum leads me to refer to a singular fact, 

 namely, tat individual plants of certain species of Lobelia, 

 Verbascur and Passiflora, can easily be fertilised by pollen from 

 a distinct pecies, but not by pollen from the same plant, though 

 this pollei can be proved to be perfectly sound by fertilising other 

 plants or species. In the genus Hippeastrum, in Corydalis as 

 shown by Professor Hildebrand, in various orchids as shown by 

 Mr. Scott ind Fritz Miiller, all the individuals are in this peculiar 

 condition. So that with some species, certain abnormal in- 

 dividuals, ind in other species all the individuals, can actually 

 be hybridsed much more readily than they can be fertilised by 

 pollen froi the same individual plant ! To give one instance, a 

 bulb of Hppeastrum aulicum produced four flowers ; three were 

 fertilised >y Herbert with their own pollen, and the fourth was 

 subsequenly fertilised by the pollen of a compound hybrid 

 descended from three distinct species : the result was that 

 " the ovarBS of the three first flowers soon ceased to grow, and 

 after a fev days perished entirely, whereas the pod impreg- 

 nated by he pollen of the hybrid made vigorous growth and 

 rapid prog-ess to maturity, and bore good seed, which vegetated 

 freely." JV^r. Herbert tried similar experiments during many years, 

 and always with the same result. These cases serve to show on 

 what slight and mysterious causes the lesser or greater fertility of 

 a species 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, Petunia, 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 widel/ dissimilar in general habit, "reproduces itself as 

 perfectly as if it had been a natural species from the mountains 

 of Chili." 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 hybr .d between Rhod. ponticum and catawbiense, and that 

 this hybrid 1" seeds as freely as it is possible to imagine." Had 

 hybrids, when fairly treated, always gone on decreasing in fertility 

 in each successive generation, as Gartner believed to be the case, 

 the fact would have been notorious to nurserymen. Horticul- 

 turists raise large beds of the same hybrid, and such alone are 

 fairly treated, for by insect agency the several individuals are 

 allowed to cross freely with each other, and the injurious 

 influence of close interbreeding is thus prevented. Any one may 

 readily convince himself of the efficiency of insect-agency by 



