108 
IOWA ACADEMY OF SCIENCE 
nothing especially worthy of notice in the open and closed daughter 
skein stages and the formation of the cell plate. 
In the preparations studied no trace of centrospheres could be 
observed. This does not prove their absence, for Delafield’s Hae- 
matoxylin is not a good stain for such structures. 
ARISAEMA TRIPHYLLUM (L.) TORR. 
In studying the development of the embryo sac in this species, 
it was noticed that many of the vegetative cells in the base of the 
nucleus and the integuments were in active division. These were 
studied with the following results : 
The first indication of nuclear division is the appearance of an 
irregular network of chromatin, as in figure 13. The strands 
gradually thicken and assume at the same time a more regular 
arrangement, until, in the spireme stage, the chromatin appears 
as a single continuous ribbon (Fig. 14). So far as the observa- 
tion extended, the chromatin ribbon is always extremely irregular. 
No uniform number of loops could be observed. It shortly breaks 
up into sixteen chromosomes. No sign of early splitting of the 
chromosomes could be detected. After the formation of the spindle, 
the chromosomes assume a V-shaped form, each one adhering to 
the spindle fibers by its middle, the two ends being free. The split- 
ting of the chromosomes begins at the apex of the V (the middle 
point of the chromosome) , and extends thence to the ends, as repre- 
sented in figure 19. The daughter star, stage, daughter skein, 
and formation of the cell plate, differ in no essential respect from 
the process as described in other plants. No centrospheres could 
be made out by the use of the 1-12 and 1-16 oil immersion objec- 
tives. The material was killed and fixed in chromo-acetic acid, 
imbedded in paraffin, cut to 3 micra on a Minot rotary microtome, 
and double stained with analin-water safranin and gentian violet. 
ZEA MAYS L. 
Kernels of Indian corn were sprouted in damp sand, and the. 
root tips were cut off when an eighth to a quarter of an inch in 
length, killed and fixed in chromo-acetic acid, and sectioned by the 
paraffin method. The sections were stained in safranin-gentian- 
violet, Haematoxylin, Fuschin and Iodine Green, or Eosin. 
While in the resting stage, the nucleus appears quite homogene- 
ous, with a well defined nucleolus surrounded by a distinct hyaline 
area. The chromatin first appears as a continuous and extremely 
irregular ribbon. Before division the ribbon loops itself into eight 
