the most extensive introgression of teosinte into maize 
would not be detectable, and the lack of cytological evi- 
dence of which he speaks would have no significance. 
On the other hand, if our assumption is valid—that the 
chromosome knobs of maize have been derived from teo- 
sinte and are good indicators of teosinte admixture— 
then there is abundant cytological evidence of teosinte 
(or Tripsacum) introgression in the maize varieties of 
practically all parts of this hemisphere (5, 82, 42, 46, 58). 
There is no longer any doubt that the knobs of teosinte 
can be transferred to corn. Cytological studies by Ting 
(unpublished) of the modified strains of inbred A158 de- 
veloped by Mangelsdorf have shown that knobs have 
been introduced into various modified strains from chro- 
mosomes 1, 2, 3, 5, 8 and 9 of Durango teosinte and 
from chromosome 4 of Nobogame teosinte. 
Nor can there be any doubt that chromosome knobs 
are associated with tripsacoid characters. Mangelsdorf 
and Cameron (82) showed that in the maize of western 
Guatemala the number of chromosome knobs is asso- 
ciated with several characteristics which may have been 
derived from Tripsacum, including denting of the ker- 
nels, fibrous seminal roots, and resistance to shattering, 
lodging, and smut infection. Brown (5) found high knob 
numbers to be positively correlated with high row num- 
bers, denting, absence of husk leaves, many seminal roots 
and irregular rows of kernels, all of which are character- 
istic of Southern Dents; but he concluded that more 
data are needed before chromosome knobs can be re- 
garded as reliable indicators of Tripsacum germplasm, 
since the Northern Flints, apparently the most tripsacoid 
maize in the United States, have the lowest knob num- 
ber. Brown added a comment, however, which Ran- 
dolph, in discussing the results, seems to have over- 
looked, that the tripsacoid nature of Northern Flints 
[ 893 ] 
