F. L. Engledow 107 



from F^ was the fact that at the base of the ear they were 6-row, while 

 at the upper end they were 2 -row. In other words, they represented 

 " mosaic inheritance." 



A number of objections have to be lodged against these conclusions: 



(1) "a deux rangs" is, in such a case, too vague a description to 

 carry any strict classificatory meaning. It has repeatedly been observed 

 that the F^ plants of a 6-row x 2-row cross while invariably possessing 

 large fertile median florets, have variable laterals. The laterals may 

 all be simply large, pointed, and inflated (as compared with those of 

 genuine 2-row barley) ; but very commonly a certain small proportion 

 of them on any ear sets grains. The variability is considerable, but 

 the distinction from pure 2-row is always apparent. The descriptions 

 employed are so vague that there arises doubt as to whether the precise 

 differences between heterozygous and homozygous (2-row) were con- 

 sidered. 



(2) The proportions of types recorded for the F^ are such as do not 

 appear among the numerous other recorded results. 



Thus, 2-row : total F^ = 134 : 401 (about). 



From the statements made in the text the expectation is 



100 : 400. 



If plants of homozygous type, which owing to conditions had foiled to 

 set any lateral grains, were classed as " a deux rangs," then an excess 

 of 2-row was certain to result. Moreover if all plants having some 

 fertile lateral florets were regarded as " 6-row," this categoiy was 

 certain to include some of the heterozygotes (which are like F^) and 

 again an excess over the 1 : 4 expectation is to be anticipated. 



(3) In the text the extreme susceptibility of the sexual organs of 

 potentially fertile lateral florets has been explained. The consequent 

 variability — some fertile and some non-fertile laterals on the same ear-^- 

 is so great, and so commonly exemplified in i'^'s and F^s, that without a 

 very critical examination no conclusion as to "mosaics" seems warranted. 

 Clearly every ear which Blaringhem classed as 6-row in his F^ was not 

 a " mosaic " ; but the amount of mosaicism cannot be gauged from the 

 record " presque toutes offraient la mosaique des caracteres." 



(4) The opinion that the so-called " mosaics " were simply hetero- 

 zygotes is confirmed by the fact that grains collected from the " 2-row 

 part of the ears " and also those collected from the " 6-row part of the 

 ears," both gave all three ear-types when sown. 



