On Direct Nuclear Divisions in the Vegetative 
Mycelium of Saprolegnia. 
BY 
FRANCIS E. V. SMITH. 
With twelve Figures in the Text. 
S INCE de Bary began his well-known researches on the cytology of the 
Saprolegniaceae, this subject has been studied by many investigators, 
the majority of whom have been mainly concerned with the sexual organs. 
Those who have studied the cytology of the vegetative organs have investi¬ 
gated the phenomena associated with the formation of zoospores (Hartog, 
1887 , 1895 ; Rothert, 1890 ; Trow, 1895 ). 
Trow and Hartog both described nuclear divisions in the vegetative 
portions of the mycelium, but while Hartog saw a form of mitotic division, 
in which four granular chromosomes appeared and spindles were absent, 
Trow was unable to observe anything comparable to this, finding only 
amitosis. 
The following investigation was therefore undertaken with the object of 
ascertaining the actual process of nuclear division. 
Isolation of the Fungus. 
The fungus was found growing on flies in the pond of the Bristol 
University Botanic Garden. From the mixture of fungi present a well- 
developed sporangium of Saprolegnia was teased out with fine forceps. 
After being washed several times in distilled water it was shown on 
microscopical examination to be free from zoospores and stray pieces of 
mycelium. It was then transferred to a Petri dish containing beef gelatine 
and the dish was tilted at an angle of 30°, and thus the infusoria and bacteria 
were drawn away from the fungus (Lechmere, 1910 ), which was finally 
transferred to sterilized flies floating on well-aerated, distilled water. To 
reduce bacterial growth to a minimum the water was changed every two 
days. 
[Annals of Botany, Vol. XXXVII. No. CXLV. January, 1923.]' 
