418 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



Green Peas (Cotyledons) and Bearded Wheats, will breed true at sight, no 

 matter how mixed their ancestry may have been ; on the other hand, 

 dominant characters, like Yellow Peas and Beardless Wheats, may or 

 may not bref d true at sight. So that " whenever it is desired in a cross- 

 bred strain to fix a dominant character selection must always be made of 

 single families containing no recessive members." 



At present the pure dominants can only be distinguished from the 

 hybrid dominants by experimental breeding. 



With regard to the question of the nature and causation of dominance, 

 it is said that we have as yet no clear indication of the causes which 

 govern the same, and that, so far, the breeder has no means at his 

 disposal by which dominance can be created, modified, or controlled. 

 Abundant evidence is, however, to hand that pure breeding is not essential 

 to the constitution of dominance, but whether inbreeding may be con- 

 cerned in the matter is not yet clear. 



Another class of facts is next dealt with : i.e., when dissimilar gametes 

 meet in the process of crossing they often produce an ancient form ; e.g., 

 two modern varieties of Sweet Peas crossed together may produce the old 

 purple Sweet Pea, with chccolate-coloured standards and purple wings. 

 This is now recognised as the rationale of Darwin's "reversions on 

 crossing " ; it should, however, be carefully noted that these " reversions " 

 do not breed true, but split up into the components which produced them. 

 Allusion is made to some curious results obtained in experiments with 

 Sweet Peas. Most varieties have long pollen grains, but the white ' Emily 

 Henderson ' has usually round pollen. A few plants of this variety, how- 

 ever, were found to have long pollen, like other Sweet Peas. 



The round -pollened ' Henderson ' with pure white flowers was crossed 

 with the long-pollened ' Henderson,' also with pure white flowers, giving 

 seeds all of which produced plants bearing flowers with chocolate purple 

 standards and blue purple ivings ! This experiment was also made 

 independently by Miss E. R. Saunders, with the same result. All had 

 long pollen, showing dominance of the long character over the round. 

 The true nature of this phenomenon will no doubt become apparent in 

 the following generations, which will be looked for with interest. 



" The occurrence of these heterozygous forms concerns the practical 

 breeder very closely. The breeder may breed a new variety of value, and 

 he may be most anxious to obtain its seed pure. Year by year he selects 

 it, but every year, if it be a heterozygote, it fails to come true, because, as 

 we now see, its germ-cells do not transmit or represent the heterozygous 

 character, but merely the pure characters of its components." An illus- 

 tration of this is one of Messrs. Sutton's lavender-coloured forms of 

 Primula sinensis. " The seeds of the self-fertilised lavenders are sown 

 each year, but of the total offspring only about one-half are lavenders, 

 one-quarter being a tinged white, and one-quarter magentas." The 

 lavender is evidently a hybrid form between the tinged white and the 

 magenta, and consequently will never breed true, however long or well it 

 be selected. 



It would appear, therefore, that the only way to get all lavender 

 Primulas would be to remake the hybrid form each time by crossing the 

 tinged white with the magenta. 



