the first clue that there was only one homeolog in Trip- 
sacum for each of the maize chromosomes. 
Confirmation of this indication followed the chromo- 
some counts made by Chaganti for individual plants in 
about a third of this segregating population. First, one 
of the genetic addition monosomics for WaT (62—586-20) 
which bore an ear segregating Wa! kernels at the fre- 
quency (82 per cent) that had been attributed to single 
homeolog transmission, was in fact found cytologically 
to have only one extra Tripsacum chromosome. Second- 
ly, chromosome counts in many of the other plants re- 
vealed the presence of various numbers of unmarked 
'Tripsacum chromosomes in addition to those which rep- 
resented homeologs of the seven recessively marked 
chromosomes in WMT maize (Table V). Since three of 
the 10 maize chromosomes were unmarked by recessive 
genes, the counts of extra Tripsacum chromosomes have 
to be considered accordingly. For example, plant 62— 
582-27 carried 18 extra Tripsacum chromosomes and 
seven dominant markers leaving not less than three nor 
more than six unmarked addition chromosomes; Plant 
62-588-65 carried 12 addition chromosomes with only 
three dominant markers leaving six to nine unmarkable 
chromosomes; Plant 62-586—48 carried five addition 
chromosomes with no dominant markers, leaving two to 
five of the unmarkable type. 
If we assume that there is in Tripsacum a genom of 
nine unmarkable chromosomes and a genom of nine 
markable chromosomes for which two markers are lack- 
ing in the WMT stock, then we can calculate the num- 
ber of unmarked chromosomes to be expected in the 
population of 168 extra Tripsacum chromosomes listed 
in Table V. This turns out to be 100; the actual number 
found was 85. The value of Chi-square for the ratio is 
5.82 which represents a P value of less than .02. 
[ 804 | 
