the discovery of alleles, previously unknown, at the 7'u 
locus, the most useful of which is the intermediate allele 
tu*. By incorporating the two higher alleles in the series, 
Tw and tu", into a uniform inbred strain (A158) through 
repeated backcrossing, it has been possible to produce 
six distinct genotypes as follows: TuTu, Tutu’, Tutu, 
tu’tu’, tutu, tutu. A comparison in a large number of 
characteristics of these six genotypes has now been made 
and the data have been briefly summarized in a prelim- 
inary statement (16) and will be reported in detail else- 
where. It can be said here that a comparison of the six 
genotypes, which are isogenic except for the T'u-tu locus, 
provides a clearer understanding than we have had before 
of what these genes actually do. And what they do is 
both remarkable and highly significant with respect to 
gaining a conception of corn’s evolution under domesti- 
cation. Dataon several of the characteristics which were 
studied are presented in Tasie 1. They show that in 
proceeding through this series of six genotypes in the 
direction from 7% 7T'u to tutu the following changes oc- 
cur: (a) A decline in the prominence of the terminal 
inflorescence, the tassel, and a corresponding increase in 
the development of the lateral inflorescence, the ear. 
(b) A change from a predominantly pistillate tassel to a 
wholly staminate one. (c) A progressive decrease in the 
length and weight of the glumes and a corresponding 
increase in the size and weight of the rachis. 
All of these profound changes are of a kind which 
might have occurred in evolution under domestication ; 
all of them tend to make the corn plant less able to sur- 
vive in the wild and more useful to man. It is important 
to note, for example, that reduction in the weight of the 
tassel has been accompanied by an increase approximately 
five times as great in the weight of the ear, the food-stor- 
age organ. Likewise, the reduction in the pistillate 
[ B41 ] 
