ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
75 
cells of multicellular spores. In all cases the septum exhibits a simple 
central pore traversed by a string of protoplasm of uniform breadth. 
The protoplasm of the string was frequently seen to be of a granular 
structure. The pore is not formed by resorption of a portion of the 
membrane, but exists from the first. This is especially well seen in 
young cultures of Achorion Schoenleinii, and was also evident in cell- 
formation by budding. In a number of filiform Algae — Spirogyra, 
Ulothrix , (Edogonium — protoplasmic connection between the cells was 
also established. 
The septum does not arise from a circular thickening of the side- 
wall, gradually penetrating into the cell-cavity ; but a new membrane 
is formed round the protoplasm-body, apparently from its parietal 
utricle ; and, as the protoplasm becomes constricted, this follows its 
contour, until, when it finally divides, each daughter-cell is surrounded 
by its own layer of cellulose. The layers of which the membrane of 
filiform Algae are composed are * so many special membranes, which 
belong to the successive encapsuled generations of cells. 
From the absence of these protoplasmic connections in those 
organisms in which each cell is independently nourished — Oidium and 
some filiform Algas — the author concludes that they are the agents for 
the transport of food material, by means of which the granular proto- 
plasm is carried from cell to cell. This was observed directly in the 
mycele of Eurotium repens. 
Pectic Substances in Tissues/ — M. L. Mangin recapitulates the 
conclusions arrived at in previous papers respecting the constant 
presence of pectic substances in the tissues of plants, and the part which 
they play in the composition of the cell-wall. When a new cell-wall 
has been completely formed, it always possesses a central lamella com- 
posed of insoluble pectates and destitute of cellulose, flanked on each 
side by secondary lamellae composed of cellulose and pectic substances. 
The formation of intercellular spaces in tissues is explained by the 
readiness with which pectic acid is transformed into isomeric substances 
which are more or less readily converted into mucilage. These spaces 
are frequently clothed with a layer of calcium pectate, probably formed 
by a filtration through the cell-wall resulting from osmotic pressure. 
The insoluble pectates form a cementing substance by which the par- 
ticles of cellulose are held together during the formation of the cell- 
wall. The dissociation of tissues may be effected by organisms which 
are nourished by pectic substances, such as Bacillus amylobacter . 
Silicified Thickening of Cell-wall.f — Herr A. Zimmermann finds 
in the epiderm of the leaf of Cyperus alternifolius , peculiar projections, 
usually hemispherical and of circular or elliptical outline. They occur 
especially on the side-walls, and frequently extend to several cells. 
They consist almost entirely of silica, with a matrix of cellulose, and 
contain no lime. The author regards them as a transitional structure 
to true cystoliths, which have not yet been found in Monocotyledons. 
* Journ. de Bot. (Morot), vii. (1893) pp. 325-43 (2 pis.). Cf. this Journal, 1893, 
p. 495. 
f Beitr. z. Morph, u. Phys. d. Pflanzenzelle (Zimmermann) (1893) p. 306 (1 fie;.). 
See Bot. Centralbl., lv. (1893) p. 211. 
