ear, are some of the specimens of ‘‘Maiz Amargo”’ from 
the province of Entre Rios in Argentina, collected and 
described by Ing. Urbano Rosbaco (50). When grown 
in Massachusetts, plants of this maize, like those of Cho- 
coceno of Colombia, have numerous tillers, hispid leaf 
sheaths and thick, drooping leaves. In Argentina, Maiz 
Amargo is somewhat resistant to the attacks of grass- 
hoppers, and this fact, coupled with the resemblance of 
some of its ears to segregates of maize-teosinte and maize- 
Tripsacum hybrids, led Ing. Rosbaco to suspect contam- 
ination with Tripsacum, perhaps the South American 
species 7. australe. Horovitz and Marchioni (17) had 
earlier suggested that the resistance of Maiz Amargo to 
grasshoppers may be due to Tripsacum introgression. 
There is still some confusion about the origin of Maiz 
Amargo. Rosbaco mentioned several references to it 
which state that it was introduced into Argentina from 
the maize-growing region of the Danube. Rosbaco con- 
siders this unlikely, and, since the tripsacoid segregates 
are extremely late in maturity, it does not seem possible 
that they could have been introduced from the Danube 
region, to which only varieties of relatively early matu- 
rity are adapted, although the original variety which sub- 
sequently became contaminated with Tripsacum may 
have been. 7". australe has not been reported from Argen- 
tina, but it has been collected in the Parana River basin 
in Paraguay, not far north of Entre Rios (10). 
We have only one determination of chromosome knob 
number in Maiz Amargo which shows it to be low, five. 
This is the lowest knob number which we have found in 
any tripsacoid maize and is consistent with the hypothe- 
sis of introgression from 7’. australe, which has been re- 
ported to have knobless chromosomes (15) or, occasion- 
ally in some forms, a small number of chromosome 
knobs. Ting (unpublished) has found up to six knobs 
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