sense that each stock may have had a different 'Tripsa- 
cum chromosome. She (21) explained that it was impos- 
sible to determine how many of the seven were really 
different. Randolph (82) stated positively that the stocks 
were trisomic for seven different Tripsacum chromo- 
somes. Maguire’s results justify her cautious statement 
that the seven stocks were ‘‘possibly’’ distinct. She stated 
repeatedly that her Tripsacum chromosomes number 4 
and 5 were very similar to one another and that they re- 
sembled B-chromosomes, although the Tripsacum parent 
had only 86 chromosomes and the corn parent had no 
B-chromosomes. In addition, her numbers 2, 6 and 9 
were similar to each other in size, morphology, behavior 
and effect on pollen sterility. We venture the opinion 
that her seven stocks contained no more than four differ- 
ent Tripsacum chromosomes, possibly even fewer. A final 
conclusion on this question must await better evidence ; 
in the meantime, there is serious doubt that Tripsacum 
contains seven different chromosomes, all without pheno- 
typic expression in the presence of two corn genoms. 
In this connection, a brief review of unpublished ex- 
perimental results obtained by Reeves on a population 
of corn-Tripsacum hybrids may be useful. During the 
season of 1955, 45 hybrid plants of Texas Inbred 203 
diploid T'ripsacum dactyloides, backcrossed three times 
to Inbred 203, were grown. Cytological examination 
was made on 17 of them taken at random, and each plant 
examined contained one extra chromosome, sometimes 
with additional irregularities. None of the 45 plants de- 
hisced any pollen. When anthers of each plant were dis- 
sected for pollen examination, no more than a dubious 
trace of starch was found in any of the many thousands 
of grains examined, and about 99 per cent of them were 
completely empty. The greatest number of seeds pro- 
duced by any of the 45 plants was 98, and the average 
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