1904] CURRENT LITERATURE 315 
see how this follows, for in all the simple solutions used there was a lack of the 
other salts normally present in the Knop’s solution. Thus, in the study of these 
poisons more than one factor has been varied. The strengths of solution used 
are throughout stated in percentages, and the obsolete method of isotonic coeffi- 
cients is used in calculating osmotic pressures, so that it will be necessary to trans- 
form the data to more modern terminology before they can be of wide use in com- 
parison. The methods and terminology of physical chemistry are most suitable 
for this sort of investigation. The general results of this part of the paper are 
as follows: Production of new motile cells can take place only with a reduction 
of the concentration of the medium. The process is checked by the presence of 
many substances, and these act chemically rather than osmotically, 7. ¢., they 
act like poisons. 
The zoospores of this alga are positively phototactic towards blue light of 
hot too great intensity, but after a limiting intensity is passed they are negatively 
80. They are sensitive to very weak light. It would be well if such observations 
as these could be made with a photometer, such as a silver salt perhaps, so that 
limits of light intensity might be definitely stated. The chemotactic responses 
of these same cells were also investigated, as were also those of Euglena gracilis, 
but the results cannot be stated here.—B. E. LIVINGSTON. 
THE EXPERIMENTAL morphology of Achlya polyandra has been studied, 
albeit in a somewhat medieval way, by Horn,3° working in KiEss’s laboratory 
at Halle. He shows that the presence of metals in the nutrient medium, as well 
a of traces of metallic salts, has a marked effect on both vegetative and reproduc- 
le activity of this organism. In such media the hyphae, which are normally 
Without cross walls, develop such walls, often at regular intervals, and the fila- 
ment often becomes divided up into polyhedral chambers, like irregular paren- 
chyma, by walls in all directions. The same effect is brought about by partially 
0 tag healthy hyphae and then returning them to the normal medium. 
Fe appears to be a difference in the nature of the cross walls in these two 
cag produced by a metal are not doubly refractive and consist largely 
» While those produced by plasmolysis are anisotropic and contain much 
te aa eres the latter form of walls is at first exactly like the former; 
to that ce appears later. The general response of the plant is quite parallel 
which I have obtained in Stigeoclonium,37 the formation of cross walls 
Bites Experimentelle Entwicklungsinderungen bei Achlya polyandra de 
* Mycol. 2: 207~2 ZS. 2T. 190 
ert tlie effect of external osmotic pressure upon Stigeoclonium see LIVING- 
AZ. 30: 361-377. pl. 22. 1900. Also, Further notes on 
of polymorphism in 
ten. fuller disc 
- Bot, Garden 
