221 
Some recent work on the cytology of fungus 
reproduction, II. 
By 
J. RAMSBOTTOM, 
Department of Botany, British Museum, London. 
In the first article of this series 1 ) the results of cytological investi¬ 
gations published during the year 1911 were considered. Certain papers were 
unintentionally omitted and accounts of them are here incorporated with 
the idea of making the series as complete as possible for the use of 
those interested in this branch of the subject. A section of the fungi 
which abound in interest are the Archimycetes, a group of microscopic 
fungi which usually infect water plants, and which are remarkable for the 
little vegetative structure they possess. As in the case of many simple 
organisms a controversial point is whether they are primitively simple or 
simple by reduction. Barrett (1912) has worked at three species of 
Olpidiopsis , 0. vexans (= 0. Saprolegniae A. Fisch.), and 0. luxurians 
Cornu. The zoospores are biciliate having two equal cilia arising from 
the same point. One cilium, in motion, trails behind, and, crossing the 
upper end of the zoospore at an angle, and leaving it usually at the side, 
gives it the appearance of the short lateral cilium that has been described 
in this and in some other closely related genera. There is present a 
type of diplanetism, a phenomenon common in the zoospores of the 
Saprolegniineae. The zoospore penetrates into the host and is, after a 
brief time, lost to view. Its individuality is maintained, however, and it 
gives rise to a single sporangium, there being no plasmodium formed. 
The young parasite is uninucleate, but soon the nucleus divides rapidly 
and the organism becomes multinucleate. Fragmentation of the protoplasm 
is believed to be simultaneous throughout the sporangium. The resting- 
spores arise sexually. The larger oogonium and the smaller adjacent 
antheridium are at first naked but soon surround themselves with cell 
walls which become fused at the point of contact. Both cells contain a 
number of nuclei, twenty-five to thirty in the youngest oogonia seen, 
though the number in the later stages is not stated. The contents of the 
antheridium pass through a small fusion pore into the oogonium, which 
soon closes up by the growth of the surrounding wall. “There is no 
contraction of the oogonial protoplasm to form an oogonium and no 
apparent changes comparable to those taking place in oogenesis in the 
higher Oomycetes .There is no apparent difference in the male and 
female nuclei, and this fact, coupled with their extremely small size, makes 
it impossible to definitely follow their subsequent relation to each other. 
However, there are indications which strongly suggest a fusion of nuclei.” 
After fertilization the oogonium becomes the oospore directly. The resting 
nucleus possesses a deeply-staining, somewhat prominent nucleolus, a 
slightly granular nucleoplasm, and a rather indistinct network with frequent 
1) See My col. Centralbl. 1912, 1, 202—207, 259—267. 
