SOME OF THE PRINCIPLES OF PLANT- BREEDING 



69 



prevented, but that the hybrids have been bred to 

 the same type as nearly as is the case in any ordi- 

 nary race or variety. 



Selection of vegetative parts. 



No consideration of the methods of plant-breed- 

 ing would be complete without a mention of the 

 improvements which can be produced by what may 

 be termed the selection of vegetative parts. While, 

 in general, all buds of a plant are practically the 

 same, as is shown by the fact that buds taken from 

 the Baldwin apple almost uniformly produce Bald- 

 win apples, yet there is considerable variation 

 frequently in the product from different buds, and 





Fig. 88. The roeueing, or removing of undesirable plants. 

 These are cotton-fields. The upper picture shows men at 

 work pulling out the plants that are not wanted; the lower 

 picture shows a field af tei* rogueing has been completed. 



it is well known that we have a class of variations 

 which we have come to call bud-sports or bud-vari- 

 ations. In violets, for example, the propagation is 

 normally by slips that are developed from different 

 buds. These slips when grown into plants frequently 

 show considerable difference, and Dr. B. T. Galloway 

 and Mr. P. H. Dorsett, of the Department of Agricul- 

 ture, have demonstrated that, by the selection of slips 

 from plants which are very productive, the yield in 

 the number of flowers to the plant can be increased 

 considerably. In the case of the orange, seedling 

 trees are almost always very thorny, yet certain 

 branches may show a tendency to be more nearly 

 thomless, and by the selection of buds from such 

 branches the thorny character of almost all the 

 standard varieties has been reduced. By the sys- 

 tematic selection of vegetative parts, such as buds. 



slips, suckers, and the like, in many cases very 

 important improvements could doubtless be secured, 

 and the plant - breeder should have a thorough 

 understanding of this method of improvement. In 

 hybrids of mixed parentage frequently a bud on 

 one side of a plant will sport, showing different 

 tendencies, and many of our new varieties of roses, 

 chrysanthemums and carnations have been pro- 

 duced by the selection of such bud-sports. Many 

 standard varieties of carnations have produced bud- 

 variations that have proved valuable ; the Lawson 

 has given rise to the Red Lawson and White 

 Lawson. The Enchantress has produced the Pink 

 Enchantress and White Enchantress. The practice 

 of exercising care in choice of chrysanthemum or 

 carnation cuttings and of cions for fruit trees is 

 therefore seen to rest on rational reasons. 



The variations in the character of the seed from 

 different bolls in the case of hybrid cottons, re- 

 ferred to on page 58, are bud-variations of this 

 sort which, as pointed out there, may be of value 

 to the breeder even in cotton which is propagated 

 by seed. In the study of cotton, the writer has 

 found similar bud-variations showing in the lint 

 characters of hybrids. In quite a number of in- 

 stances, certain bolls have been found which pro- 

 duced much longer lint than other bolls on the 

 same plant, and similar variations in strength and 

 uniformity of length have been observed. Experi- 

 ments indicate that such variations, which are 

 doubtless to be classed as bud-variations, are trans- 

 mitted in considerable degree. This being the case 

 even in seed-propagated plants, it becomes desirable 

 to observe and search for bud-variations. 



Literature. 



The principal general works are : Bailey, Plant- 

 Breeding, 4th edition, 1906, The Macmillan Co., 

 New York ; Frnwirth, Die Zuchtung der Land- 

 wirtschafllichen Kulturpflanzen, Berlin, 1904-06. 

 The following are a few of the most important gen- 

 eral papers : Production et iixation des variet6s 

 dans les vggetaux, E. A. Carriere, Paris, 1865 ; 

 Die Pflanzenmischlinge, W. 0. Focke, Berlin, 1881; 

 A Selection from the Physiological and Horticul- 

 tural Papers of Thomas Andrew Knight, published 

 in the Transactions of the Royal and Horticultural 

 Societies, London, 1841 ; Hybrids and Their Utili- 

 zation in Plant-Breeding, W. T. Swingle and H. J. 

 Webber, Yearbook, United States Department of 

 Agriculture, 1897; Sur la production et la fixa- 

 tion des varietSs dans les plantes d'ornement, Jean 

 Baptiste Verlot, Paris, 1865 ; The Improvement of 

 Plants by Selection, H. J. Webber, Yearbook, 

 United States Department of Agriculture, 1898 ; 

 Hybrid Conference Report, Journal Royal Horti- 

 cultural Society, Vol. XXIV, April, 1900 ; Survival 

 of the Unlike, Bailey; Proceedings, International 

 Conference on Plant-Breeding and Hybridization, 

 New York Horticultural Soc. Memoirs, Vol. 1, 1902; 

 Proceedings of American Breeders' Association, 

 Vols. I and II, Washington, D. C, 1905 and 1906; 

 Breeding Animals and . Plants, W. M. Hays, St. 

 Anthony Park, Minnesota. Bailey's Plant-Breeding 

 contains a very extended list of papers and books. 



