420 BOTANICAL GAZETTE [may 



article that the writer is very reluctant to discard them. A safe 

 tentative conclusion would be the following. The prime requisite 

 for mottling is that the R factor enter with the male parent only; 

 this perhaps is equivalent to saying "that the R factor be present 

 in the endospenn in just one out of three possible doses." Under 

 these circumstances mottling regularly occurs when there is also 

 present that condition which is possessed and transmitted by most 

 C tester individuals. A different condition, occurring in R tester, 

 favors mottling in a small percentage of the possible cases, while 

 the conditions present in East's material permit of no mottling 

 under any circumstances. The critical data should, of course, 

 appear in the next generation. 



Partial variability 



The term "partial variability" has been used to indicate the 

 variation which may occur between different parts of a single plant 

 as regards any given character, without implying anything about 

 the mechanism which may 'explain this variation. It is therefore 

 preferable to "somatic segregation" for the present purpose. 

 Preliminary tests of the possibility of partial variability in corn 

 were conducted in two very simple and obvious ways. The first, 

 so far as it went, gave such decisive and orthodox results that it 

 may be summarized very briefly. With respect, at least, to the 

 P, R, and C factors, pollen from suckers that had been allowed to 

 develop was identical in crosses with that obtained from the main 

 plant. Ears developed on such suckers were, if present, so poorly 

 developed as to yield no adequate ratios; but ears produced on 

 suckers that had been allowed to develop abnormally, through 

 early removal of the main stem itself, gave the predicted ratios 

 in all cases. These results discouraged carrying out any large 

 scale test of this matter, at least as regards aleurone color. On the 

 other hand, a few sporadic cases suggest that such manipulation 

 might yield surprising results when applied to the inheritance of 

 plant color, and particularly chlorophyll. The other method was 

 to apply the same pollen to the silks of two of the ears on the same 

 individual, and to compare the ratios obtained. Such attempts 

 were frequently unsuccessful, owing to the inability of the plants 



