182 BOTANICAL GAZETTE [MARCH 
to cap either pole of the nucleus( fg. zz) of a cell cut somewhat 
obliquely, the cytoplasmic aggregations appearing to extend over 
and around these segments (see also fig. 24). In such figures 
the clear space presents the same appearance and the same stain- 
ing reaction as the nuclear interior. 
A study of the nuclei in the prophase stages did not furnish 
satisfactory evidence that such hyaline segments capping the 
nucleus are regular stages in the formation of the achromatic 
figure. Although such appearances are to be frequently met with 
in material fixed in chrom-acetic, similar nuclei in the prophase 
show no hyaline sphere segments, but merely enlargements with 
cytoplasmic polar aggregations. Hence a question can be raised 
as to the existence of the hyaline polar caps in the living cells. 
Is this appearance a normal phenomenon produced by a with- 
drawal of cytoplasm from the pole of the nucleus, and to be 
referred to. the turgescence of the living cell which causes the 
formation of a plasma membrane around the nuclear membrane? 
Or has this appearance been caused by fixation, the nucleus hav- 
ing become distorted and the membrane split or swollen? Or, 
thirdly, are these polar caps only optical effects resulting from 
looking down upon sections of an irregularly shaped nucleus, the 
lower boundary being projected beyond the upper boundary and 
hence producing the appearance of polar caps? A section of 
a nucleus shaped like a truncated cone can be conceived as pre- 
senting such an appearance, 
In order to solve this problem, examination was made of 
many preparations fixed and stained by the methods previously 
outlined. If the hyaline caps are not produced by fixation, or 
are not optical effects produced from looking down upon sections 
of an amoeboid-shaped nucleus, but, on the contrary, are normal 
phases in the growth of the achromatic figure, their presence 
should be established in similar prophase stages and in all fixa- 
tions which otherwise preserve the character of the cell contents. 
Preparations fixed in chrom-acetic showed such phenomena 
frequently, but by no means so constantly as to warrant their 
being considered a normal feature of division. Figs. 7g and 2° 
represent a periblem cell drawn at upper and lower focus and 
