143 
in proportion to the completeness of the sulphonization, e. rj ., the blue 
GB, a mixture in which trisulphonated triphenylrosanilin predominates, 
is the most active of the soluble blues. The second group is formed 
by the alkaline salts of rosolic acid, which stain callose and cellulose 
directly. Finally, the third group, the eosines, or salts or fiuorescine 
such as eosine, erythrosine, and phloxine, stain nitrogenous matters 
deeply, but are not fixed by callose or cellulose. 
As various stains of the aromatic series also combine with nitrogen¬ 
ous substances, to avoid error it is often indispensable that there should 
be a mixture of several reagents belonging to different categories. 
This gives a very demonstrative double stain. 
(3) The constitution of the membrane of fungi is still unknown. The 
author believes that fungine and metacellulose do not exist as specific¬ 
ally distinct substances. The membrane of fungi is so complex and 
variable that it would be possible to offer the chemical composition in 
evidence whenever the absence of fructification rendered the determi¬ 
nation of families uncertain. 
In the group under consideration the membrane is composed of cal- 
lose and cellulose closely associated. To show this, leaves containing 
Peronospora ficaricv may be treated as follows: 
(a) Treat Avith concentrated chlorhydric aeid; (b) macerate for some 
minutes in Schweizer’s reagent. This removes all the cellulose and 
pectin compounds contained in the host and in the parasite. After 
washing in water, the use of iodated phosphoric acid or of the benzidine 
colors does not reveal a trace of cellulose in the tissue of the leaf, but 
the reagents of callose bring out a network of mycelial filaments. Con- 
trarywise, if we submit the contaminated leaves of the Ranunculus to 
the action of Hofmeisters’s clilorated mixture* and after washing allow 
the tissues to macerate in a solution of potassa or caustic soda, renewed 
several times, all the callose is removed Avithout sensible modification 
of the cellulose. Then by the use of iodated reagents we can see the 
mycelial filaments stained blue or violet in the midst of the disasso¬ 
ciated tissues of the host plant. 
Thus either the cellulose or the callose can be removed without chang¬ 
ing the form and arrangement of the mycelium. But while cellulose 
and callose are always associated in the organs which the parasite sends 
into the host (mycelium and oospores), the conidiophores are formed of 
pure cellulose. This is proved by their disappearance after the action 
of cellulose solvents. 
The mycelial membrane varies in thickness and shows numerous lay¬ 
ers, but what gives the mycelium of the Peronosporime a special char¬ 
acter is the constant presence of masses of callose, which is either pure 
or associated with cellulose. These constrict the cavity of the tube or 
even obliterate it. In the latter case, they form the so-called septa. 
These masses are seen very clearly in Peronospora parasitica , P. Schlei- 
cJenij P. myosotidis , Plasmopara viticola , etc. They serve very clearly 
