BRASSICA CROSSES. 



By ARTHUR W. SUTTON, F.L.S., V.M.H. 



IN 1899 I was attracted to the study of crosses among species and varieties of 

 Brassicas by a statement in one of the leading agricultural journals that certain 

 types mentioned by the writer do not hybridize naturally, and therefore can be 

 grown in close proximity to each other without fear of destroying the highly 

 selected forms which the seedsman is at so much pains to keep true. 



As experience gained during many years' association with practical seed-growing 

 convinced me that the statement was incorrect, I decided to put the matter to 

 a practical test in order to place on record the results obtained, and to show which 

 species and varieties of Brassica would intercross and which would not. 



In the first experiments, begun in 1900, the varieties of Brassica oleracea, L., 

 shown in figs. 1 to 9 (PI. 1), were planted side by side so that cross-fertilization 

 might take place wherever such was possible. (For names of these varieties 

 see list on page 10). 



The seed saved from these plants gave rise to an extremely heterogeneous 

 collection of nondescript forms, few or none of which were true to the female 

 parental type. Various types, however, were noticed which there was every 

 reason to believe would, if it were possible to perpetuate them, become valuable 

 additions to the economic plants of the farm or garden. From these the forms 

 represented in figs. 10, 11, 12, & 13 (PI. 2) have been fixed, and come fairly true 

 from seed. 



In a later season the experiment was repeated with the addition of varieties 

 of Turnips (Brassica Rapa, L.), Swedes (Brassica campestris, L., var. Napo- 

 brassica, DC.), and non-bulbing oil-yielding Rape (Brassica campestris, var. 

 oleifera, DC.). 



Instead, however, of all being planted in one large patch, they were arranged 

 in small isolated groups of seven plants each. Two of the plants were of one 

 variety, and round them were placed five of another kind. In this manner about 

 twenty such double combinations were arranged and the seed saved and grown. 



A large collection of mongrel plants was obtained ; the results were entirely 

 in accordance with my previous experience, and proved that while no variety 

 derived from Brassica oleracea was affected by the pollen of Rape, Swede or 

 Turnip, and vice versa, yet all the types of B. oleracea would freely intercross 

 between themselves, and this was equally true of many varieties of Turnip, Swede, 

 and Rape. 



Hitherto I had been content to note such species of Brassica as would 

 intercross when planted in close association, but looking over the plants raised 

 in the last experiment with Professor Percival of University College, Reading, 

 we concluded that the experiment would be far more complete if a series of carefully 

 controlled artificial crosses were undertaken in order to ascertain whether some 



