May 17,1924 
Chfomosomes in Maize and Maize Relatives 
679 
hybrids resulting from crosses between plants having different chromosome 
numbers. 
The presence of trivalent chromosomes at diakinesis of the pollen mother-cell 
recalls the studies of Belling (2), in which he reports that, in polyploid forms, the 
chromosomes combine not only to form bivalent, but also tri valent, tetravalent, 
and even pentivalent groups. The random distribution of the undivided uni¬ 
valent chromosomes at the heterotypic anaphase of the pollen mother-cell devel¬ 
opment in this corn-teosinte hybrid is similar to that described by Sax (21) for 
the hybrids of Triticum monococcum X T. turgidum. 
The possible identification of the univalent chromosomes present at meiosis 
in E. perennis X Zea mays hybrids is suggested by a study of the pollen where the 
corn involved was of the Chinese waxy type. The pollen in this cross had only 
4 per cent of the grains showing erythrodextrin. There is also a very small 
percentage of meioses in which there are no extruded chromosomes. This may 
indicate that the extruded chromosomes are contributed to the hybrid by the 
waxy corn parent. This is contradictory to the chromosome behavior in the 
pollen mother-cells of a Nicotiana hybrid described by Goodspeed (9 ), where the 
bivalents were probably made up by a union of chromosomes from the two parents 
and the univalents were the leftovers from the parent with the larger chromosome 
number. The division of the univalent chromosome at the heterotypic division 
in this Nicotiana hybrid is unlike that found in teosinte-corn hybrids and similar 
to that described by Sax (21) for hybrids between the emmer and the vulgare 
groups of Triticum. 
The study of the Tripsacums has shown that in this genus the haploid chromo¬ 
some number is approximately 35. The reduction divisions of all Mexican forms 
studied resemble minutely that described by Bremer (5) for several varieties of 
Saccharum officinarum. In the Tripsacums, as in S. officinarumj chromosomes 
failed to fuse at diakinesis and the resulting univalents lag on the spindle. The 
division of lagging univalents occurs in the heterotypic division and this asso¬ 
ciated with a varying number of univalents in different pollen mother-cells makes 
exact chromosome counts very difficult. 
SUMMARY 
The chromosomes of Euchlaena perennis pair promptly at diakinesis of the 
pollen mother-cell, giving 20 bivalents. 
The chromosome number of Euchlaena mexicana at diakinesis of normal¬ 
appearing pollen mother-cells is 10 bivalents. Occasionally 11 or 12 chromosomes 
have been found in reduction phases that appeared abnormal. The mother-cell 
tissue in anthers of this species is frequently in a multinucleated mass and very 
abnormal in appearance. 
The chromosomes of Zea mays , strains Tepic and Chinese waxy, pair promptly 
at diakinesis of the pollen mother-cell, giving 10 bivalents. 
The chromosomes of Zea mays X Euchlaena mexicana pair promptly at diakine¬ 
sis of the pollen mother cell, giving 10 bivalents. 
The chromosomes of Zea mays X Euchlaena perennis combine at diakinesis 
of the pollen mother-cell into trivalent or bivalent chromosomes or remain 
uncombined as univalents. The number of chromosome elements is 30, the sum 
of the haploid number of the two parents. The distribution of the 30 chromosome 
elements at meiosis is very irregular. 
The chromosomes of Coix lachryma jobi pair promptly at diakinesis of the 
pollen mother-cel], giving 10 bivalents. 
