May 17,1924 
Chromosomes in Maize and Maize Relatives 
677 
Coix lachryma jobi L. 
Table II also shows interesting pollen counts in two coix plants the pollen of 
which was segregating for the waxy-starchy character. The most significant 
thing noticed in these counts was the condition in S. P. I. No. 48867 where the 
number of grains showing erythrodextrin was double that showing starch. The 
high per cent of sterility allows for a 1:1 segregation of waxy and starchy grains, 
but the death rate in starchy grains must have been much higher than in the 
waxy. The presence of such a large per cent of erythrodextrin grains suggested 
the possibility that the segregation had been other than a 1:1 ratio as might occur 
if there were two factors controlling the expression of the character. 
The chromosome number was determined for S. P. I. No. 48867, the coix plant 
showing the unexpected high per cent of grains staining red. The haploid num¬ 
ber is clearly 10 (PI. 2, C, F, G, I, and L). This number had previously been 
determined for coix by Kuwada ( 14 , 15). 
Plate 2, J, was prepared to show the similarity between the 10 chromosomes 
of the two maize varieties studied and coix. This comparison of the chromo¬ 
somes of maize and coix is introduced to show that the variation in the size of 
the individual chromosomes of coix are as great as those in maize. Kuwada (13) 
considers that a possible origin of the two large chromosomes in all 10-chromo- 
somed corns is through a fusion of two chromosomes derived from a 12-chromo- 
somed ancestor. The writer is of the opinion that 10 is the basic chromosome 
number for the Tripsaceae, and this view is supported by the similarity between 
the 10 chromosomes of corn and the 10 chromosomes of coix. 
Tripsacum. 
Tripsacum is less closely related to either Zea or Euchlaena than these two 
genera are to each other. Attempts to cross Zea and Tripsacum (8) have failed 
thus far. This investigation has revealed a very different chromosome complex 
in Tripsacum from that found in corn or in teosinte. 
The haploid chromosome number for all Tripsacums examined appears to be 
35. Plate 3, C and D, are drawings of a nucleus from T. dactyloides. The 
chromosomes were separated in about two equal portions by the microtome 
knife, the two sections showing 35 bivalent chromosomes. It is assumed that 
the fragment at the right in Plate 3, C, was cut from one of the chromosomes of 
Plate 3, D. Plate 3, E and F, represent the equal distribution of the chromo¬ 
somes in the pollen mother-cell divisions. Such divisions are characteristic for 
all T. dactyloides material studied. 
Plate 3, A and B, represents the condition in two phases of the heterotypic 
division of pollen mother-cells from T. laxurn growing at the department green¬ 
house, Washington, D. C. These plants were grown from seed collected in Sal¬ 
vador. There are 36 chromosomes in the diakinesis pictured, but two of these 
have the appearance of univalents. The heterotypic anaphase pictured shows 
the irregular division of the chromosomes; 30 bivalent chromosomes have 
divided and are at the poles, while 10 univalent chromosomes are at the nuclear 
plate region in the process of division. The division of lagging univalent chromo¬ 
somes at this time makes it necessary to study the early reduction phases in order 
to determine the chromosome number for forms characterized by such a division. 
Other drawings (PI. 3, H and I) show irregularities in the pollen formation 
of two Mexican Tripsacums. The cytological material for a study of these two 
forms was collected in Mexico by Messrs. Collins and Kemp ton in the fall of 19 23 
These figures demonstrate that the irregularities in chromosome distribution 
during meiosis are not due to greenhouse conditions. 
