16 



HORTICULTURAL SOCIETY OF NEW YORK. 



in the third generation of any hybrid that obeys Mendel's law. If by growing your 

 wheat, your mother plants, for three generations, you find they do come true to type, 

 then they are true to type. 



H. F. Roberts: How about mutation forms? 



W. J. Spillman: I can't see that mutation forms have any particular bearing on this 

 subject, as concerns any variety which we are considering a fixed variety as far as its 

 being a hybrid is concerned. Maybe they are mutation forms, and I imagine that when 

 we have come to examine a larger number of plants with reference to the mutations 

 which are called to our attention, we will find them probably more common than we 

 have anticipated. Yet I cannot avoid throwing out this word of caution: I may be 

 wrong myself in it. This matter of hybridization is separate from mutation. We may 

 liave mutations in our homozygotes and we may have mutations in a hybrid plant, so 

 that we must not confuse them. When wc are dealing with hybrids let us overlook the 

 mutations that occur. Now, there is a general belief that hybridization stimulates varia- 

 tion. That is a point which seriously needs investigation. I can see no reason why it 

 should do so. For instance, Perrin, in Australia, speaks of the second generation of 

 wheat as the variable generation. I object to the word variable in that generation, 

 because it is not variability; it is simply splitting up in obedience to a definite, well 

 known law, and a splitting up in a way that can be predicted. 



There has been an enormous amount of w-ork done on hybridization in the past, 

 and Sachs, in the edition of his book published, I think, in 1879, went so far as to state 

 that the whole question was definitely settled, and that all that could be learned had 

 been learned then. The enormous amount of effort that has been put upon hybridization 

 before has been an effort to discover what that heterozygote would be, what characters 

 would be dominant, and they have been trying to determine laws by which they can 

 predict what will be a dominant and what will be a recessive character in hybrids. 1 

 think I am not misrepresenting the facts in the case. Now we have learned that there is 

 apparently no settling that; so that question we let alone. We wait until we get our 

 hybrid; after we have it w^e can tell just what we will get ultimately, and the test of the 

 law is our ability to prophesy by it. Now I want to repeat a statement which I have 

 made twice before in public, that in the case of those characters which do obey Mendel's 

 law— and the number is increasing rapidly, as Professor Bateson has said — we can abso- 

 lutely state in advance, before we make a hybrid, what the result will be. That seems 

 like a very astounding statement, but I agree with a statement of Professor Bateson 

 already published, and which I have along with mc, in which he says that he regards 

 Mendel's discovery as of equal importance with the formation of the atomic theory in 

 chemistry. 



William Saunders: In regard to the lengLn of time which it will take to fix a 

 particular species, I will cite an example which we had at the experimental farm in 

 Ottawa. We imported a wheat from near Spitzbergen, near the Lena River, which was 

 said to be a fixed type and had been in cultivation there from time immemorial. This 

 wheat we grew for two or three years, examining it very carefully without observing 

 any sports of any kind in it. Of course, there might have been sports, and we might 

 have overlooked them; but it was examined carefully for two or three years. Subse- 

 quently to that, bearded sports made their appearance in this wheat. The wheat was so 

 small in the kernel that rhere was no probability of our having confused that with any 

 other variety of w heat. We bred from those sports bearded forms of that wheat, although 

 the beardless was the form in which we received it. It was an exceedingly early wheat, 

 too, so that the probabilities of any confusion arising from any intermixture were less 

 than if they had all bred at the same time. 



W. J. Spillman: In that case it is possible that the bearded heads were pure 

 snorts, irrespective of any hybridization that the wheat had experienced in the past. 

 That is possible, and is something that we cannot avoid in any way. We may select a 

 type for an indefinite number of years, and then occasionally get a sport from it, due to 

 something that we do not understand. 



William Saunders: The selection of types for purposes of hybridization was under 

 discussion, and this case shows the possibility of such types varying even after three 

 years. 



