320 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
with inanimate material, both absorb moisture more rapidly from a 
humid atmosphere and loose it more slowly in a drying atmosphere. 
9. The sap of these terrestrial algse is highly concentrated — so much so 
after a little evaporation that further loss of moisture is prevented. 
The rate of drying of the different forms varies much, the Hormidium 
stage of Prasiola being slowest. Thus terrestrial algae are well equipped 
to face vicissitudes. Actual desiccation does not take place, since the 
air-dry cells retain a good proportion of moisture. And this retention 
of moisture is presumably due to the highly concentrated cell -sap ; but 
the absence or paucity of vacuoles may mean that much of the sap is 
held adsorbed by colloidal constituents within the protoplast. The 
granules (reserve-bodies) of these algae may be due to the peculiar con- 
ditions in the protoplasts as a result of the absence of vacuoles. Possibly 
too they are part of the mechanism for retaining moisture in the cells. 
A. G. 
Fixation of Nitrogen by Green Plants. — F. B. Wann ( American 
Journ. of Bot., 1921, 8, 1-29, 1 pi. 1 fig.). An account of experiments 
that show that some Chlorophyceae can utilize nitrogen from the 
atmosphere. This they do when grown on mineral nutrient agar 
containing a nitrate and glucose. If the carbohydrate be absent very little 
atmospheric nitrogen is fixed ; and this fixation ceases when organic 
nitrogen is supplied. The algal fixation of nitrogen compares favourably 
with that recorded for nitrogen-fixing bacteria. A. G. 
Method of Healing in some Algal Cells. — Susan P. Nichols 
(American Journ. of Pot., 1922, 9, 18-27, 1 pi.). An account of 
experiments made in wounding mature cells of certain algae (Nitella, 
Ohara , Vaucheria, Cladophora , Chaetomorpha ), and of the results observed. 
All but one of the species studied are able to heal a wound. The 
protoplasmic density in some species is very liquid and varies up to a 
quite viscous condition in other species. No correlation was found to 
exist between the protoplasmic density and the character of the cell wall. 
The exuded protoplasm may or may not be miscible with water. If the 
exuded protoplasm be non-miscible, the film formed over the escaping 
protoplasm is not comparable with the plasma membrane. The wound- 
puncture is not closed by a film or membrane, but by an accumulation 
of the plastids, pyrenoids, and starch granules in the opening. A new 
plasma membrane grows inward from the old membrane and separates 
a portion of the protoplasm, filling the puncture from the remainder of 
the cell. A new wall is gradually formed by this membrane, and the 
healing is complete. A. G. 
Reproduction of Vaucheria by Amoeboid Zoospores. — A. de 
Puymaly (Comptes Rendus , Paris, 1922, 174, 824-7). In 1879 Stahl 
(Bot. Zeit ., 37, p. 129) announced a remarkable mode of reproduction 
in Vaucheria geminata , in which a large number of amoeboid zoospores 
escape from the mother-cell, creep about for a time, then round themselves 
off, develop a cell wall, and finally germinate and produce a new 
individual. This observation had not been followed up. But last 
February the author found V. hamata growing on sand near Bordeaux, 
which in the greener part of its feltwork showed regularly segmented 
