May 17,1924 
Chromosomes in Maize and Maize Relatives 
675 
while all grains without protoplasm, and therefore sterile, remained unstained. 
The table also summarizes the chromosome condition found in 20 heterotypic 
prophases of 9 of these hybrid forms. 
Table I.— Records of pollen and pollen formation studies in Euchlaena perennis X 
Zea mays 
Plant name 
Plant 
No. 
Pollen counts 
Heterotypic prophase chromosome 
condition 
Fertile 
Ster¬ 
ile 
Blue 
Bed 
Clear 
Tri¬ 
va¬ 
lent 
Biva¬ 
lent 
Uni¬ 
va¬ 
lent 
Remarks 
Z. mays x E. perennis: 
Female parent— 
Oregon Evergreen. 
Th. 
102 
290 
330 
S. P~ I. 51291.. 
Th. 
103 
175 
356 
Missouri Cob Pipe. 
Th. 
79 
4 
7 
6 
Do. 
Th. 
79 
118 
114 
4 
6 
6 
Crinkly... 
Th. 
82 
69 
119 
3 
7 
7 
E. perennis x Z. mays: 
Male parent— 
Brachytic crinkly tassel 
seed.. 
Th. 
87 
174 
121 
1 
9 
9 
Do. 
Th. 
87 
174 
121 
1 
9 
9 
Pod. 
Th. 
88 
3 
7 
7 
Do. 
Th. 
88 
3 
7 
7 
Do. 
Th. 
88 
3 
7 
7 
Do. 
Th. 
88 
4 
6 
6 
Do....... 
Th. 
88 
5 
5 
5 
Do... 
Th. 
88 
1 
9 
8 
Shows only 29 
units. 
Crinkly lineate. 
Th. 
92 
109 
209 
2 
10 
4 
Do. 
Th. 
92 
109 
209 
2 
10 
4 
Dwarf. 
Th. 
93 
2 
3 
18 
Early prophase. 
Brachytic dwarf.. 
Th. 
94 
4 
5 
8 
Brachytic liguleless ramose 
Th. 
95 
3 
9 
3 
Do. 
Th. 
95 
4 
7 
4 
Do....... 
Th. 
95 
7 
4 
1 
Chinese waxy. 
Th. 
96 
296 
13 
96 
10 
10 
Do. 
Th. 
96 
296 
13 
96 
2 
9 
6 
A study of the pollen mother-cell development in these hybrids showed that 
the attempt to combine the 10 chromosomes from the corn parent and 20 chromo¬ 
somes from the teosinte parent gave varying counts. The author for some time 
found it difficult to determine the chromosome number. The difficulty was due 
to an irregularity in chromosome fusion and also to the fact that the chromosome 
number for Euchlaena perennis had not been determined at this time. Finally it 
was found that there are three classes of chromosomes at diakinesis (PI. 1, E, F, 
and G), trivalents, bivalents, and univalents. It required practice and good 
material to segregate the chromosomes according to the above classes, but counts 
at diakinesis and the heterotypic metaphases gave uniformly 30 chromosome 
units. 
Table I shows the condition found in 20 nuclei selected from different hybrids. 
The figures are taken from drawings made of characteristic and clear heterotypic 
phases. A minute study of trivalent chromosomes at this stage shows that 
many have a large part corresponding to a bivalent chromosome and a small, 
loosely attached portion. In a few cases the tri valent chromosomes seem to be 
composed of three loosely and temporarily attached chromosomes. The author 
considers that these loosely attached chromosomes are univalents which for 
a short period unite with bivalents or with each other to give trivalent or perhaps 
bivalent chromosomes. 
96037—24f-6 
