ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
215 
Internal Structure of the Cell- wall.* — Herr C. Correns has in- 
vestigated the inner structure of the cell-wall, chiefly in Algoe belonging 
to the CladoplioraceoB, Bryopsideae, and Valoniaceee. He does not find 
in these Algte different systems of striation in the same lamella. Stra- 
tification depends on differences in the amount of water contained in the 
tissue ; each lamella consists of two layers, a dense and a soft one. 
Striation is due, on the contrary, to a delicate folding of the lamellae ; 
each lamella is folded in one direction only, while the folds in two 
contiguous lamellae are usually at right angles to one another. The 
readiness with which the lamellae break up into fibres is due to their 
being differentiated, parallel to the folding, into striae of different chemi- 
cal and physical properties. The striation is the result of a process of 
growth, the innermost and youngest lamellae appearing to be unstriated. 
The inter-crossing of the different systems shows that the folding cannot 
be due to external mechanical forces. 
In the Characeae the phenomena appear to be the same as in the 
classes of Algae mentioned. In Trentepohlia there is a very peculiar 
structure of the cell-wall, the striation depending on cushion-like 
thickenings which arise centrifugally. In the Floridese the striation 
depends, as in most Chlorophyceae, simply on a folding of the membrane. 
In Bornetia secundiflora the cell-wall encloses masses of protoplasm, 
which form threads running within or on the surface of the denser 
lamellae near to the septa. 
Taking the whole vegetable kingdom, striation may be due to four 
causes, viz.: — (1) differences in the amount of water contained in smooth 
lamellae (bast-fibres of Apocynacese, cuticle of the leaf of Hyacinthus) ; 
(2) a delicate folding of the denser lamellae (cell-walls of Cladophoraceae, 
Yaloniaceae, &c.) ; (3) a delicate centripetal thickening of the wall 
(tracheids of Coniferae, hairs of Cereus) ; (4) a delicate centrifugal 
thickening of the wall ( Trentejpohlia , hairs of Urtica , and those on the 
filaments of Narthecium ossifragum). 
Crystallization of Cellulose and Chemical Structure of the Cell- 
wall.f — M. E. Gilson has succeeded in crystallizing cellulose within 
the vegetable cell, by dissolving in cupric ammonium oxide and precipi- 
tating by ammonia. The aggregates of crystals are spherocrystalline or 
dendritic according to the concentration of the ammonia, and are ren- 
dered more visible by staining with chlor-zinc-iodide or congo-red. 
They exhibit all the characteristic reactions of cellulose. The authors 
obtained them from all membranes which are coloured blue by chlor- 
zinc-iodide, and from no other. They were procured also from the cel- 
lulose of Tunicates, but not from the cell-wall of Fungi. The reserve- 
cellulose appears to be a mixture of true cellulose and other carbo- 
hydrates. 
The author distinguishes three distinct lamellae in cell-walls, the 
middle lamella common to contiguous cells, an intermediate, and an 
inner lamella. Since the crystals are always formed in the interior of 
the cell, he concludes that the innermost lamella is always rich in cellu- 
lose ; the intermediate lamella consists of cellulose and other substances, 
* Beitr. z. Morph, u. Phys. d. Pflanzenzelle (Zimmermann), i. (1893) pp. 260-305 
(2 pis. and 1 fig.). f La Cellule, ix. (1893) pp. 397-441 (l pi.). 
