The Present Position of Cell-Wall Research. 161 
the lignin-reactions is.an hadromal-cellulose-ether together with a 
trace of free hadromal. Maule has described a reaction for 
lignified tissue which can still be obtained after the abstraction of 
hadromal. He concludes from this that Czapek’s hadromal cannot 
be the true lignin but is only a constant concomitant of this. It 
should be mentioned, however, that Czapek himself had suggested 
that more than one cellulose-ether may possibly occur in lignified 
membranes. The membranes of Fungi have been the subject of 
careful examination by Gilson, Winterstein and Van Wisselingh. 
Cellulose and chitin are the most important constituents. These 
two bodies do not occur together but each is usually accompanied 
by other, generally undetermined or little known substances ( e.g. 
lichenin). Cellulose was only detected in (1) three Peronosporeae 
which were examined ; (2) Saprolegnia; (3) A few Myxomycetes. 
A small quantity of cellulose may possibly exist in Rhitisma 
salicinum whilst in Geaster and Usnea bodies occur which react 
similarly to cellulose ( geastrin and usnein). Chitin was only rarely 
found wanting in the membranes of the higher Fungi but the 
quantity in which it occurs varies greatly. The Zygomycetes, 
Chitridiaceae, Entomophthoreae and some Myxomycetes contain 
chitin. In Bacteria, Saccharomyces, Fuligo septica and Cetraria 
islandica neither chitin nor cellulose were found by V. Wisselingh. 
Callose does not usually occur in fungal membranes. Pectic bodies 
are occasionally found; Lagerheim found these, accompanied 
probably by chitin, in the walls of the Monoblepharideae. 
An interesting contribution to the chemistry of the cell-wall in 
various Mosses is made by Czapek. He finds that the cellulose is 
seldom free in these membranes but is usually combined either with 
a phenol-like body — sphagnol —or with a tannin-like substance— 
Dicranum-tannic acid. 
After this brief review of the chemistry of the cell-wall it 
remains for us to consider the manner of its formation by the 
protoplast and its subsequent growth and differentiation. It has 
been a matter of frequent discussion whether the wall is formed by a 
direct transformation of a layer or mass of cytoplasm (Pringsheim) or 
whether it is produced by the secretory activity of the protoplast 
(Von Mohl). A large number of cases are now well established in 
which the wall is unquestionably formed on the surface of the 
protoplast by secretion. In some other cases the whole cytoplasm 
appears to become “ transformed ” into cell-wall material. This 
has been described (Strasburger, Tischler, Buscalioni, Schmitz and 
