674 
Journal of Agricultural Research 
Vol. XXVIII, No 7 
E. mexicana Schrad. Annual teosinte. 
Favorable pollen mother-cells of this species show 10 as the haploid chromo¬ 
some number (PL 2, B, E, and K), corresponding to the number determined by 
Kuwada ( 14 , Id). Plate 2, H, represents a heterotypic anaphase with 11 chromo¬ 
somes going to each pole. This number was found in a very small per cent of 
the cells studied. In the few anaphases found that had more than 10 divided 
chromosomes the extra chromosome was slow in dividing and the halves lagged 
in their movement to the poles. 
It was found in material collected for this study that the pollen mother-cells 
were very frequently abnormal in appearance; the mother-cell tissue of an 
anther was in one mass, with the nuclei dotted here and there through it. This 
mother-cell mass eventually subdivided into pollen grains, dividing first into 
polynucleated sections and finally into cells with a single nucleus. It was found 
that these nuclei contained the reduced number of chromosomes, but it was not 
determined whether such cells developed into normal pollen grains or not. 
Kuwada (IS) described a very similar abnormality in amber rice popcorn. 
He is inclined to think that this was due to insufficient nutrition. The author 
will not attempt an explanation until material grown under more favorable 
climatic conditions has been studied. 
Zea mays L. 
To the present time four varieties of corn have been examined. All show 10 
bivalent chromosomes at diakinesis. Plate 2, D, represents a typical heterotypic 
metaphase in the pollen mother-cell development of Chinese waxy maize, and 
Plate 2, A, the same phase in Tepic corn, a very large variety introduced from 
Mexico. 
The author's investigations of corn have failed to show any deviation from 10 
as the haploid chromosome number. The presence of 20 chromosomes in peren¬ 
nial teosinte and of 10 in annual teosinte and waxy and starchy corns makes it 
appear probable that the basic chromosome number in Euchlaena and Zea is 10. 
This view opposes that suggested by Kuwada (IS), that is, that the number 12 
is original for all the races of Zea mays and that Zea mays is tetraploid and 
derived from an original form which had probably 6 chromosomes in reduced 
numbers. 
EUCHLAENA X ZEA 
Zea mays X E. mexicana (F 2 ). 
The material for this study was taken from a normal and a dwarf plant in 
an F 2 progeny of a cross between E. mexicana from Chaleo, Mexico, and maize 
of the type known as dwarf (10). The chromosome number in each plant is 
10, as was determined by Kuwada for a Euchlaena-Zea hybrid (14 t 15) • No 
irregularity in chromosome distribution was observed in the pollen mother-cell 
development. 
Zea mays X E. perennis. 
A dozen or more of these hybrids had been made in 1922, and a morphological 
and cytological study was made of the pollen development in F x plants of nearly 
all of these. Table I shows pollen counts of mature pollen from seven represen¬ 
tative F t hybrids. These counts were made from pollen stained with chloral- 
hydrate-iodin solution (water 50 cc., chloral hydrate 50 gm., iodin 1 gm., 
and absolute alcohol 50 cc.). The pollen was taken from anthers just before 
they opened. At this time grains containing protoplasm, and therefore seemingly 
viable, stained deep blue or red, due to the presence of starch or erythrodextrin, 
