NOTES ON Mendel's methods. 15 



illustrates once more the thorougl: and painstaking methods by which Mendel 

 overcame all obstacles in his pursuit of truth. 



To sum up the methods of Mendel : Those hybridists who desire to follow 

 in the footsteps of Mendel and his disciples and help to elucidate the bafflino- 

 problems of inheritance will find it essential to select parents for the original 

 cross which possess characters which are at once Single and Constant and 

 Differential and Dominant, and they must also take care to raise large nniiibers 

 of individuals in many generations for observation and comparison. By these 

 methods alone will definite results be obtained. 



In conclusion, as a practical illustration of Mendel's methods, a list is oiven 

 of his own selection of characters in the Axed races of Garden Peas that he 

 used for his experiments. 



PisuM Sativum. 



(Fixed Races of Garden Peas.) 

 Mendel's 



Characters. Dominant X Recessive. 

 (i) Form of Ripe Seeds Round X Wrinkled. 



(2) Color of Cotyledons Yellow X Green. 



(3) Color of Seed-Coat I rr^rve]-^te,] I Brown X White. 



(3) Color of Flowers. . . i ^01 related ^ p^^pj^ ^ ^^^.^^^ 



(4) Form of Ripe Pods Inflated X Wrinkled. 



(5) Color of Unripe Pods Green X Yellow. 



(6) Position of Flowers Axial X Terminal. 



(7) Length of Stem 6 — 7 ft. X ^ — 114 ft 



H. F. Roberts: I am engaged in wheat breeding, and I should like to inquire 

 whether (considering the fact that wheat hybridizes) one can assume in making the first 

 hybrid that we have a succession of pure bred parents; or whether it will be necessary 

 to make such a succession of pure bred parents, bringing them into existence by hand 

 fertilization, in order to be certain that we have a pure bred parent. Is it safe to assume 

 that one already has such pure bred parents? 



The Chair: Will Professor Bateson kindly answer the question of Professor Roberts? 

 It is this: Whether, in making wheat hybridization, we are to assume that we have a 

 parentage on either side that is pure, or must we produce this ourselves by hand fer- 

 tilization for a number of generations before we can confidently proceed with our antici- 

 pated results? 



W. Bateson: It is difficult to speak on a subject of which I have no practical 

 knowledge. My knowledge of wheat breeding is derived from reading the work of others, 

 and also from some experiments that I have seen which have been conducted by Mr. 

 Bififen, of Cambridge. Mr. Biflfen holds, I believe, that the wheat is likely to hybridize, 

 and I should imagine it is rash to infer that what one finds to be true of one variety 

 would be true of another. I imagine that one would have, in any case of this kind to 

 begin by selection from any selection of plants, and then satisfy one's self that they were 

 breeding pure and producing one form. 



L. H. Bailey: Professor Spillman, who has had practical experience in that line, 

 is here, and I should like to hear from him on this subject. 



W. J. Spillman: I can only say a few words on the subject. The difficulty to which 

 our president called attention a moment ago exists in the case of seed wheat. You may 

 have a beardless variety of wheat, and there will be a small amount of bearded with it, 

 which will appear in that variety every year. That is because you have that typical 

 heterozygote; you have a small amount of it in your seed wheat, and if it is necessary 

 to be sure it is necessary for you to grow your wheat and select the type for three 

 generations. You may then be practically certain that you have a pure type. 



H. F. Roberts: Not scientifically certain? 



W. J. Spillman: Well, as near as you can ever be. In fact, you can, if you use 

 proper methods. We can eliminate the old method of fixing a type by selection. In 

 fact, tliat does not fix a type, as has been brought out here. But you can fix your' type 



