ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
81 
Position of the Chromatophores in the Palisade Cells of Marine 
Florideae and G-reen Foliage. — G. Senn ( VerhancU . Naturforsch. 
Gewllsch. Basel- , 1916, 28, 104-22, figs. ; see also Bot. Gentralbl. , 1919, 
140, 242). In the palisade cells of Peyssonnelia Squamaria and 
Plato ma cyclocolpa , the chromatophores in diffuse illumination of 
moderate intensity are ranged in antistrophe on the transverse walls 
towards the source of light. By illumination of the under side of the 
thallus of Peyssonnelia , the chromatophores are obliged to collect 
together in the lower ends of the cells, which then are the best lighted. 
Apostrophe is brought about in the cells of Platoma through prolonged 
deficiency of light, parastrophe through intensive illumination. The 
difference between the position of the chromatophores in the palisade- 
cells of marine algas (antistrophe) and of green leaves (epistrophe) in 
optimum diffused illumination is caused by the difference of th optical 
conditions. Under certain treatment antistrophe can be brought about 
in foliage also. The occurrence of palisade parenchyma in marine algae 
does not appear to be an adaptation to diffuse illumination, as in green 
foliage, but it is caused by the special growth conditions of the thallus. 
E. S. G. 
On the Gelose of Certain Florideae. — Camille Sauvagea* 
(. Bulletin de la Station biologique d'' Arcachon, 1921, 18* annee, 113 pp. > 
Some Bed Algae when boiled in water yield a carbohydrate which jellifies 
upon cooling. These algae are discussed, and the preparation and 
characters of the jellies are described. These are of three types : — 
1. In Gelidium and some eight other genera the decoction, even when 
very dilute, sets into a jelly upon being cooled. Some of their cell- 
walls can be stained by a solution of iodine, owing to the presence of a 
substance comparable with amyloid. 2. In Chon dr us and seven or 
more genera the decoction sets in a mass if well concentrated, or, if 
diluted, it sets under the action of certain electrolytes. The walls do 
not stain with iodine. 3. In Polyides and four other genera the jellifi- 
cation is intermediate between the other two types ; aluminium sulphate 
has a particularly coagulating action upon it : the cell-walls are 
permeable to carbohydrate, and in general are insensitive to iodine. 
European species of Gelidium are as valuable as those used by the 
Japanese for making “kanten” (agar), but are more scarce. If 
Japanese agar were pure its jellifying properties would be still more 
accentuated. The bleaching of algae in the open air, as done in Brittany 
and Ireland, often damages the material. Artificial bleaching is not 
much employed. When boiled sufficiently, the mucilage of Ghondrus 
is nearly colourless, whether the plants have been bleached in the open 
air or not ; the colour of material which has been artificially bleached 
by sulphurous acid or by sodium bisulphite is generally darker ; and 
“ phycocolle,” which is darker-coloured than mucilage, becomes quite 
decolorized in a solution of potassium chloride without losing its 
properties. 
Many of the particularities in the chemical or histo-chemical nature 
of the cell-membrane have yet to be studied. The cellulose of Gelidium 
and Gracilaria (the only genera examined by the author) resists the 
action of cupro-ammonia. In the pectic or cellulosic parts of certain 
G 
