248 PRODUCTION OF HYBRIDS. 



516. The Production of Hybrids. If the pollen of one species is 

 employed to fertilize the ovules of another, the seed will often produce 

 plants strictly intermediate between the two parents. These are termed 

 hybrids, and are analogous to mules in the animal kingdom. As a 

 general rule, hybrids can only be produced between plants which are 

 very nearly allied, as between different species of the same genus. 

 Thus, different species of Heath, Fuchsia, Cereus, Rhododendron, and 

 Azalea, readily inoculate each other, and produce intermediate forms. 

 It is found, however, that species which seem to be nearly related do 

 not hybridize. Thus, hybrids are not met with between the Apple 

 and Pear, between the Goosberry and Currant, nor between the Rasp- 

 berry and Strawberry. The ovules of Fuchsia coccinea, fertilized 

 with the pollen of Fuchsia fulgens, produce plants having intermediate 

 forms between these two species. Some of the seedling plants closely 

 resemble the one parent, and some the other, but they all partake more 

 or less of the characters of each. By the examination of the foliage, 

 conclusions may be drawn as to what will be the character of the flower. 

 Mr. Thwaites mentions a case in which a seed produced two plants 

 extremely different in appearance and character ; one partaking rather 

 of the character of Fuchsia fulgens, and the other of Fuchsia coccinea. 



517. In the case of hybridization, there appears to be a mixture of 

 matters derived from the pollen-grain and the ovule, just like the 

 mixture of two endochromes in flowerless plants ; and the nature of 

 the hybrid depends on the preponderance of the one or other. Some 

 have supposed that the pollen-grains require to be of the same form 

 and dimension, in order to admit of artificial union taking place ; but 

 this is a mere conjecture. Hybrids perform the same functions as 

 their parents, but they do not perpetuate themselves by seed. If not 

 absolutely sterile, at first, they usually become so in the course of the 

 second or third generation. Herbert mentions instances of hybrid 

 Narcissuses, from which he attempted in vain to obtain seed. The 

 cause of this sterility has not been determined. Some have referred it 

 to an alteration in the pollen. Hybrids may be fertilized, however, 

 by the pollen taken from one of the parents, and then the offspring 

 assumes the characters of that parent. 



518. Hybrids are rarely produced naturally, as the stigma is more 

 likely to be affected by the pollen of its own stamens than by that 

 of other plants. In dioecious plants, however, this is not the case, 

 and hence the reason probably of the numerous so-called species 

 of Willows. Hybrids are constantly produced artificially, with the 

 view of obtaining choice flowers and fruits, the plants being propa- 

 gated afterwards by cuttings. In this way many beautiful Roses, 

 Azaleas, Rhododendrons, Pansies, Cactuses, Pelargoniums, Fuchsias, 

 Calceolarias, Narcissuses, &c., have been obtained. By this process of 

 inoculation, and carefully selecting the parents, gardeners are enabled 



