FERTILISATION AND HYBRIDISATION 37 



them to be really modified leaves) they are replaced by petals, as in the 

 garden Eose (p. 382), Carnation (p. 240), Hollyhock (p. 272), Double 

 Begonia (p. 462) and Chrysanthemum (p. 531). The more the stamens 

 and pistils become suppressed or modified by cultivation, the less chance 

 is there of obtaining seeds from such flowers, and plants bearing them 

 are with difficulty increased by seeds. Hence the adoption of other 

 methods of propagation in such cases. 



FERTILISATION AND HYBRIDISATION 



Since the functions of the stamens and pistils have been better 

 understood, gardeners have taken full advantage of them by transferring 

 the pollen from the stamens of one flower to the pistils of another with 

 a view to raising new races or ' strains ' as they are called. When in a 

 reciprocal state, fertilisation is usually effected, the pollen grows on the 

 sticky surface of the pistil (called the stigma) and seeds are ultimately 

 borne in the way described at p. 24. The plants raised from such 

 seeds may combine the characters of both parents in a more or less 

 even degree. When two species of the same genus are thus fertilised 

 a ' hybrid ' is the result. When two species belonging to different 

 genera are fertilised, the product is called a ' bigeneric ' hybrid. But 

 when forms of the same species are fertilised with each other, they are 

 simply called ' crosses,' and chiefly differ in the colour and size of the 

 flower. 



Of late years hybridisation has been carried on to an enormous 

 extent among all classes of plants, and some very fine garden flowers 

 have been thus obtained. It must be remembered, however, that only 

 plants having a natural relationship to each other are likely to produce 

 hybrids. The more distantly related they are, the less likely are they 

 to be fertilised or produce seeds. As most of the plants described in 

 this work are arranged according to their natural relationships to each 

 other, it will be easy to see which are the most likely ones to use for 

 hybridising purposes. 



Unlike animals, it is a remarkable fact that most plant hybrids are 

 capable of producing fertile seeds, and are as perfect in every detail as 

 the species from which they were origmally derived. Occasionally a 

 hybrid is met with, which only with difficulty can be fertilised and made 

 to produce seed. In such a case as with ' double '-flowered plants it 

 must be increased by other means than seeds. 



It may be appropriate to mention here that certain flowers, like Prim- 

 roses (p. 617), Auriculas (p. 618), Oxalis (p. 292), Loosestrife (p. 461) &c. 

 have the stamens and pistils alternately long in some flowers and short 



