PRODUCTION OF HYBEIDS. 297 



with those of the other, giving rise to a germinating body. In 

 Phanerogamic plants, also, there are two cells with different contents 

 — the pollen-grain with its granular fovUla, and the ovule with its 

 protoplasm. These are brought into connection by means of the 

 poUen-tube, formed from the intine, which either enters the embryo- 

 sac, or comes into contact with it, the union taking place either 

 directly by its extremity, or indirectly by cellular prolongations 

 from the conducting tissue, or from the ovule. By this means the 

 formation of the embryo is determined, which commences as a cellular 

 body or germinal vesicle, in the interior of which other cells are sub- 

 sequently formed in a definite order ,of succession. 



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

 employed to fertilise the ovules of another, the seed wUl often pro- 

 duce plants 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 the different species of the same genus. 

 Thus, different species of Heath, Fuchsia, Oerens, Rhododendron, 

 and Azalea, readily inoculate each other, and produce interme- 

 diate forms. It is found, however, that many plants which seem to 

 be nearly related do not hybridise. Thus, hybrids are not met 

 with between the Apple and the Pear, between the Gooseberry and 

 Currant, nor between the Easpberry and Strawberry. The ovules of 

 Fuchsia coccinea, fertilised with the pollen of Fuchsia fulgens, pro- 

 duce 'plants having intermediate forms between these two species. 

 Some of the seedling plants closely resemble the one parent, and 

 some the other, but they aU partake more or less of the characters of 

 each. By the examination of the foliage, conclusions may be drawn 

 as to what wiU be the character of the flower. Mr. Thwaites men- 

 tions 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. While hybrids 

 are produced between two species, crosses are produced between two 

 varieties. 



In the case of hybridisation, 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 poUen-grains require to be of the same form 

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

 this is a mere conjecture. It is, however, requisite for successful 

 hybridising, that the pollen should be in a state of fuU maturity, and 

 the stigma perfect. Hybrids perform the same functions as their 

 parents, but they do not perpetuate themselves by seed. They must 

 be propagated by offsets or cuttings. If not absolutely sterile at first, 



