66 
Smith.—On Direct Nuclear Divisions in the 
number of nuclei in this part was between 270 and 280, while the num¬ 
ber of uninucleate zoospores was about 280 ; this shows that no nuclear 
divisions take place in the sporangium. 
The cytoplasm in the upper parts often appears frothy. Through¬ 
out the plant are found occasional granules of the cellulose-like substance 
to which Pringsheim gave the name of cellulin, since it gives most of the 
reactions of cellulose. 
The nuclei are very numerous in the hyphae, but always occur in much 
Fig. 1. The apical sporangial region of a hyphal filament, showing the dense cytoplasm, s.c ., and 
spherical nuclei, z, zoospore, x 500 and x 1,500. 
Fig. 2. The middle portion of a hypha, showing two kinds of cytoplasmic strands and 
elongated nuclei. Most of the nuclear divisions occur in this region. d.n ., dividing nucleus; 
c., cellulin body, x 500 and x 1,500. 
greater numbers towards the tip, whither they are carried by the rapidly 
streaming cytoplasm. The typical nucleus is spherical in shape, but both 
shape and size vary according to the position in the plant (Figs. 1-3). 
The main portion of the nucleus consists of a central body which stains 
very deeply with all nuclear stains. Surrounding this is a layer of nucleo- 
hyaloplasm which is bounded externally by a distinct nuclear membrane, 
which in all good preparations is found to be of uneven thickness, due 
to the presence of granules of chromatin ; these granules are not evenly 
distributed, but usually appear as occasional mounds upon the nuclear mem¬ 
brane (Figs. 4 and 5). The central body is suspended within the nucleus by 
fine linin threads arising in most cases from the chromatin granules on the 
