26 HYBRIDISING AND SELECTION 



var. atropurpurea, "Swat Magret," etc., whose purple is of a deeper 

 shade than that of the original tree. Andre's broom, with its maroon 

 wing petals, is a similar instance ; most of its seedling progeny are more or 

 less reversions towards the common Cytisus scoparius. 



(3) The hybridisation of two plants of varying character is the quickest 

 and surest means of producing new forms under cultivation. One is 

 certain of getting something new, even if it be something in no way 

 superior to either parent, and often the breeder can form some idea of 

 what he is likely to obtain. We undoubtedly owe our most valuable 

 garden shrubs to hybridisation, sometimes by human, sometimes by insect 

 agency. The garden races of rhododendron and azalea, roses and clematis, 

 and such beautiful plants as Berberis stenophylla. Magnolia Soulangiana, 

 Salix Salamoni, Cytisus kewensis and C. Dallimorei^ Spir&a arguta and 

 Hypericum Moserianum, are a few examples of those which have had 

 their origin in the intentional or sometimes accidental crossing of species. 

 Hybrid trees and shrubs have usually a vigour superior to that of either of 

 their parents. As this is work which any amateur may do, it will be worth 

 while to devote a few words to the operation of hybridising itself. 



The first equipment of the operator is a true understanding of the 

 structure of the flowers to be operated on. Ordinarily, a flower consists 

 of sepals, petals, stamens, and pistil, which may be regarded as of two 

 sections: first, the protective or ornamental; second, the essential or 

 sexual parts. The first or outer section consists of calyx (or sepals) and 

 corolla (or petals), sometimes calyx alone. They play no part in the 

 production of seed; their purpose is to protect the sexual parts when 

 young, and later, by displaying bright colour, to help to advertise the 

 flower and attract the notice of insects to fertilise it. That function 

 performed, their work is done, and they usually fall away. The real 

 reproduction of the plant by seed is accomplished by the stamens (male) 

 and the pistil (female). The process of fertilisation or impregnation is 

 brought about by the transference of pollen (usually a minute yellow 

 powder borne in sacs called anthers at the top of the stamen) to the 

 summit of the pistil. The pistil has three parts ; -at the base is the ovary, 

 a swollen body which contains the incipient seeds, or ovules ; above that 

 is a stalk of varying length called the style, bearing at the top a knob 

 (ultimately viscid), called the stigma. It is upon the stigma that the 

 pollen must lodge so that the ovules may be changed into fertile seeds. 



Whilst Nature adopts various methods to prevent the fertilisation of 

 a flower by its own pollen (often by the non-synchronous ripening of the 

 pollen and receptivity of the stigma ; often by separating the sexes on 

 different plants), her intention is that the impregnation should be done 

 by pollen from a flower of the same species. Thus whilst, in the higher 

 groups, she abhors in-breeding, she also objects to mules. The hybridiser, 



