ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
637 
Plasmolysis and the Protoplasmic Membrane.* — Prof. R. Chodat 
and M. A. M. Boubier have made experiments on plasmolysis in a number 
of plants belonging to various classes of Cryptogams (Algse, Muscineas, 
fern-prothallia), as well as on flowering plants. The following is a 
summary of the conclusions arrived at. 
In isolated cells the plasmolysed protoplasm does not become com- 
pletely detached from the cell-wall ; it remains for a time connected 
with it by more or less numerous threads of ectoplasm. These threads 
have no connection with the filaments of protoplasm which pass through 
the cell- wall. Their formation is explained by the viscid consistence 
of the ectoplasm, and by the fact that the limiting layer of the proto- 
plasm passes insensibly into the cell-wall, and may give rise, by appo- 
sition, to new layers. The adhesion of the ectoplasm to the cell- wall 
partly explains its passivity in the protoplasmic movement. The ecto- 
plasmic layer (parietal utricle) cannot be regarded., as some authors 
have done, as a sharply differentiated structure, a distinct organ. In 
many gelatinous Algae it passes insensibly into the cell-wall ; while 
it is also continuous with the granular protoplasm, to which it adheres 
more strongly than to the cell-wall. 
Structure of the Cell-wall.f — Prof. E. Strasburger gives the result 
of fresh researches, especially on the following points : — The formation 
of the division-walls in the pollen-mother-cells of Lilium and Alstroe- 
mevia ; the formation of a membrane round isolated protoplasm-balls 
in Vauclieria ; the formation of the beams of cellulose in Caulerpa ; the 
formation of sacs in the epiderm of the seeds of Cupliea ; the formation 
of the massulm-chambers and glochids in Azolla ; the development of the 
extine of pollen-grains of Knautia and Althaea ; the stratification of 
the pith-cells in the stem of Clematis. The following are the results 
already attained. 
The materials of the cell-wall are products of the protoplasm. They 
are either excreted on the surface of the protoplasts (division-walls in 
pollen-mother-cells of Lilium, &c., protoplasm-balls of Vauclieria ), or 
they remain in the interior of the protoplasts, and there undergo a 
variety of changes (beams of Caulerpa'). In many cases (massulse of 
Azolla) a definite mass of protoplasm is completely transformed into 
cellulose, the material for the formation of cellulose being apparently 
a product of the splitting up of cytoplasm. The cell-walls increase in 
superficies by passive traction and simultaneous apposition of new 
lamellae, or by active intussusception. Their increase in thickness in 
tissues is generally effected by the apposition of new lamellae, which do 
not further increase in thickness by active intussusception, but under- 
go changes by passive infiltration and incrustation. In certain cases, 
especially in isolated cells, a secondary increase in thickness of the 
lamellaB takes place by active intussusception, often accompanied by 
striking changes in form (extine of the pollen-grains of Althaea and 
Knautia). Both apposition and intussusception therefore take part, 
separately or combined, in the increase in thickness of the cell-wall. 
Instead of the terms kinoplasm and trophoplasm for constituents of 
the cell, Strasburger proposes jilarplasm and alveolarplasm. The secon- 
* Journ. de Bot. (Morot), xii. (1898) pp. 118-31 (1 pi.). 
t Jahrb. f. wiss. Bot. (Pfeffer u. Strasburger), xxxi. (1898) pp. 511-98 (2 pis.). 
