184 BOTANICAL GAZETTE [MARCH 
studied seem to preclude the possibility of mistake. Such doubts 
as were expressed in my former papers have been practically 
removed. So far as the writer is concerned, the interpretation given 
below is conclusive. Another investigator might perhaps come to 
different conclusions by using other methods. 
MATERIALS AND METHODS. 
Stamens of various ages were collected in Clay County, Kansas, 
during July 1904; killed in weak chrom-acetic acid (chromic acid 0.3%”, 
glacial acetic acid 0.7°°, water 99°‘), passed gradually through the 
grades and preserved in 70 per cent. alcohol, imbedded in paraffin, 
cut 10-18 » thick, and stained on the slide. Some old slides, the mate- 
rial of which had been killed in the ordinary chrom-acetic acid solu- _ 
tion, were also at hand. Various stains and combinations were used, 
but for bringing out the chromatin network and chromatin granules 
of the early stages, Delafield’s haematoxylin, when properly developed, 
gave by far the best results, being superior in this respect to either 
Heidenhain’s iron-alum-haematoxylin or safranin and gentian violet. 
Nucleoli, both in the nuclear cavity and in the cytoplasm, are stained 
very distinctly by the safranin-gentian-violet combination, but are 
only slightly affected by Delafield’s haematoxylin. 
_ I am indebted to my wife, MABEL ScHAFFNER, for the prepara- 
tion of most of the two hundred serial slides on which the present 
paper is based. 
INVESTIGATION. 
Before the microsporocytes are beginning to separate the promi- 
nent chromatin network is being transformed into slender delicate 
threads. These threads appear to be discontinuous in some places. 
However, the appearance may be due to injury during the process of 
cutting. The threads are small in diameter as compared with the 
single chain of spherical chromatin granules (figs. 1-3). After the 
spirem becomes fully developed it shows no free ends and is much 
wound, looped, and twisted. In this stage it appears to be entirely 
free in the nuclear cavity and is usually in the so-called synapsis stage. 
Sometimes the contraction is to one side of the nuclear cavity, some- 
times near the center, but often little or no contraction is evident. 
Whether this is an artifact or a real stage in the process of karyokin- 
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