780 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
sterigma in tlie Peronosporese, always consists originally of callose, 
to the entire exclusion of cellulose, which is only developed at a later 
period when the conid is fully formed. This callose, at first exceed- 
ingly resistant to the action both of water and of chemical reagents, is 
capable of undergoing modifications, the nature of which is at present 
unknown, by which it becomes soluble in water. On the access of water 
to the septum, this process of dissolution of the callose takes place at 
once, and the conids thus become disarticulated. 
The species most carefully examined was Cystopus candidus. The 
basid is a club-shaped cell, the Wall of which is very thick below, much 
thinner in the upper portion. When a conid is about to be produced, a 
ring of callose is formed in this upper part which is at first very thin and 
scarcely visible, but gradually becomes thinner and forms a funnel-like 
structure with the opening pointing downwards ; this opening gradually 
closes, and the upper portion of the basid is now cut off as a conid, a 
sudden narrowing taking place at the line of the septum by the absorp- 
tion of the outer cellulose- wall at that spot. The callose septum now 
assumes successively the form of a cup and of a cylinder ; and by the 
repetition of this process, a string of conids may be formed attached to 
one another by cylinders of callose, and at length set free by the 
dissolution of these cylinders. This same process appears to take place 
uniformly throughout the Peronosporese ; but is much more difficult to 
follow in the species of Plasmopara and Peronospora , and in Premia 
Lactucse. 
Penetration of the Host by Peronospora gangliformis.* — Mr. W. 
H. Rush describes the mode in which the germ-tubes of this fungus 
penetrate the epiderm of Lactuca sativa — through the stomates, and not 
through the cell- walls as stated by De Bary. The germ-tubes will some- 
times curve, apparently for the purpose of reaching a stomate. 
Biology of Phycomyces nitens.f — M. A. De Wevre has made a 
series of experiments on the growth of this fungus on bread soaked with 
various nutritive substances and under varying conditions of light and 
moisture. The following are the general conclusions at which he has 
arrived : — Solid substrata give better results than soft, and especially 
than liquid media. Phycomyces is subject to modification according 
to the nutritive medium on which it developes, in relation to its size, 
colour, branching, rapidity of growth, and the production of septa and 
swellings. Light has a tendency to diminish its size, and moisture is 
very prejudicial to its growth. 
Doassansia.J — Dr. W. A, Setchell gives a monograph of this genus 
of Ustilagineae, comprising twelve species, three of them new, which he 
arranges in three subgenera, Eudoassansia, Pseudodoassansia, and Doas- 
sansiopsis. He appends descriptions of two new nearly allied genera : — 
Burrillia , Sorus compact, not separating into its elements on being 
crushed ; central portion composed of an irregular mass of parenchy- 
matous tissue ; spores closely resembling those of Entyloma , both in 
structure and in germination, compacted into several dense rows ; cortex 
* Bot. Gazette, xvi. (1891) pp. 208-9 (1 fig.). 
t CR. Soc. R. Bot, Belgique, 1891, pp. 107-25. 
% Froc. Amer. Acad. Arts and Sci., xxvi. (1891) pp. 13-9. 
