CHAPTER III 

 HYBRIDISING AND SELECTION. 



PERHAPS the most fascinating of all branches of plant cultivation is the 

 production of new forms in the garden itself. New plants of garden 

 origin, as distinct from those newly introduced from other countries, are 

 obtained in three ways: by branch "sports," by selection among seed- 

 raised plants, and by hybridisation. So far as trees and shrubs are 

 concerned, the first process is purely accidental, the second frequently so. 



(1) Branch sports are abnormal shoots that occasionally appear on 

 adult trees or shrubs and are taken off and propagated by cuttings, buds, 

 or grafts. Many of them preserve their abnormality indefinitely, but 

 others have a strong tendency to revert to the normal type. Nearly all 

 variegated shrubs and trees, those with deeply cut leaves, and those with 

 double flowers originated as branch sports. 



(2) The production of new forms under cultivation by selection from 

 seed has given to gardens some of their most beautiful plants ; but in 

 regard to trees and shrubs (trees especially), the intervals between the 

 generations are too long for the work to attract the ordinary man as a set 

 purpose. Most new forms of seedling origin in gardens have originated 

 as chance breaks, noticed by nurserymen or others among batches of 

 plants raised to furnish ordinary stock. Most weeping, fastigiate and 

 dwarf trees have originated in this way; also purple-leaved, large- or 

 small-leaved varieties, and forms with richer-coloured or larger flowers. 

 Like branch sports, they must be increased by vegetative parts cuttings, 

 grafts, etc. and propagated in this way they show little or no tendency 

 to revert back to the normal type. Raised from seed they show a 

 strong but not a uniform tendency to revert to the parent type; thus 

 often a small proportion come true or even show the peculiarity of the 

 form to an increased extent ; a larger proportion are more or less inter- 

 mediate; the remainder will be indistinguishable from the type. The 

 purple beech is an illustration ; comparatively few of its seedlings come 

 quite true, they are mostly of an ineffective purplish green or coppery 

 hue, but a number of purple beeches have been raised from seed, such as 



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