106 P. F. Wareing and T. A. VilUers 



will germinate without after-ripening. Now, if just the chalazal re- 

 gion of the integuments is removed, the seed will not germinate. In 

 fact, if all the integuments are removed, excepting for 2 or 3 mm. at 

 the micropylar end, the seed will not develop. On the other hand, 

 if this 2 or 3 mm. portion of the integuments at the micropylar end 

 is removed, the seed will germinate even though the remainder of 

 the integuments is left intact. If you examine the peach seed mor- 

 phologically, you will observe that there are rudiments of endosperm 

 tissue immediately adjacent to the radicle, or the hypocotyledonary 

 axis in the micropylar region. When the integuments are removed, 

 this endosperm tissue comes away with it. From all of this, one might 

 speculate that an inhibitor lies in the endosperm of the peach seed 

 at the micropylar end, and he might be prompted to look for it 

 there. 



Dr. Wareing: In the case of ash, of course, the endosperm com- 

 pletely surrounds the embryo, but what Dr. Tukey said ties up also 

 with observations on Iris. Randolph and Cox (Proc. Amer. Soc. Hort. 

 Sci. 43: 284, 1943) showed that the endosperm has a very strong in- 

 hibitory effect which is probably due to a specific inhibitor. 



Dr. Evenari: I would like to compare this situation with the case 

 of lettuce seeds. Dry lettuce seeds are full of inhibitors and there 

 is apparently no promoter present. After root growth has started, the 

 inhibitors disappear and a number of promoters (the chemical nature 

 of which is imknown) appear. This disappearance of inhibitor and 

 appearance of promoters occurs quite late insofar as the germination 

 process is concerned and occurs only after germination has, in reality, 

 finished and root growth has already started. In this case, at least, it 

 will be difficult to correlate the so-called dormancy of the seeds with 

 the presence of the inhibitor. I think wc have to be careful here in 

 differentiating between what we call germination inhibitors and 

 growth inhibitors, as apparently these two are different from each 

 other. 



Dr. Wareing: First of all, when Professor Evenari speaks of pro- 

 moters, he's talking of promoters revealed in the Avena coleoptile 

 test which presumably means auxins and, therefore, I would not be 

 surprised to find no particular correlation between dormancy in let- 

 tuce seed and changes in auxins. On the question of correlations be- 

 tween inhibitors and dormancy, the whole subject is fraught with pit- 

 falls because so many things will stop Avena coleoptile growth or, 

 for that matter, will inhibit germination, and the real crux of this 

 problem is to sort out purely toxic substances from functional inhib- 

 itors. Professor Evenari said that in lettuce seed he cannot get a cor- 

 relation between the inhibitor content and the stale of dormancy. 



