DISCUSSION 
The hypothesis presented here regarding the ancient 
origin of ‘Tripsacum from an amphidiploid hybrid of wild 
maize and Manisuris is a testable one. We shall continue 
with experiments designed to test it In various ways, and 
we hope that others will also be interested in doing like- 
wise by all means, including, for example, the use of 
. 
techniques sometimes referred to as ‘chemical taxono- 
my. Virtually all of the morphological and cytological 
data which we have been able to evaluate so far is con- 
sistent with the hypothesis. An exception yet to be 
explained, however, is the fact that if the 10 pairs of 
chromosomes in modern maize are combined with the 
nine pairs of Manisuris, we might expect it to produce 
an amphidiploid with 19 pairs rather than the 18 pairs 
of Tripsacum. The most plausible explanation at the mo- 
ment is that one maize chromosome has been lost, proba- 
bly in the 2n hybrid. 
The past and possible future contributions of TPripsa- 
cum germplasm to the evolution of maize should be more 
completely evaluated. Genes forthe perennial habit, the 
immunity to some of the major fungal diseases affecting 
maize (Malm and Beckett, 1962), increased resistance to 
heat and drought, stiffer leaves and stalks (Mangelsdort 
and Reeves, 1989), early flowering and longer internodes 
above the ear position (Galinat, 1963) and increased 
vielding capacity and improved chlorophyll characters 
(Reeves and Bockholdt, 1964) are probably but a few 
of those which we might wish to transfer from 'Tripsa- 
cum to maize. 
Mangelsdorf (unpub.) has pointed out that because the 
apparent wild maize genom in Tripsacum has been sub- 
jected to some very rigorous environments for Jong 
periods of time, it may possess genes of great economic 
