332 SUMMARY OF CURRENT RESEARCHES RELATING TO 



hanging drop, they collected on the side opposite to the light. The dead 

 zoospores were, doubtless, those which had been pierced by or imprisoned 

 in the crystals formed by the low temperature. Those zoospores which 

 had been in the layer of separating water, were still in good condition. 



Chemical Stimulation of a Green Alga.*- — B. E. Livingston 

 describes his experiments on a species of SUgeoclonium and their results. 

 Thirty different reagents were tried on the filaments, and the author 

 comes to the following conclusions : Nitrate and sulphate, in the case 

 •of a large number of metallic elements, act in the same way and at the 

 same concentration upon the filamentous form of this alga. He con- 

 cludes that the stimulation is due to the cations. At high enough 

 concentrations death is produced. The change produced at somewhat 

 lowerconcentrations is strictly parallel, in form of cells and manner of 

 ■cell division, to that caused by extraction of water, or inhibition of its 

 ■absorption. At this lower concentration, and at a still lower one, there 

 is a marked acceleration in the production of zoospores. This is 

 exactly the opposite of what results from water- extraction. The 

 acceleration in zoospore activity gradually decreases with weaker solu- 

 tions until the normal behaviour is reached. The work and results of 

 •other authors are compared with the present research. 



Germination of Spores.f— F. W. Neger finds that the spores of 

 Bulgaria polymorphs germinate readily under the chemical stimulus of 

 plant-remains, such as bark, leaves, or wood of oak or pine. It is suffi- 

 cient if the bark, etc., be in the immediate neighbourhood, though the 

 influence is more marked when they form part of the culture medium. 

 He notes also the influence of temperature on germination. 



Chemical Changes. 



Action of Wood on Photographic Plates.} — H. Marshall Ward 

 refers to W. J. Russell's recent memoir,§ in which is described the 

 ■action of a number of different kinds of woods on a photographic plate 

 in the dark ; after a period of varying length, during which the smooth 

 •dry face of a wood block has been in contact with the plate, the 

 latter, on development, may show an image. Russell had suggested 

 hydrogen peroxide as the active agent, and the resin in the wood as 

 probably the indirect causal agent, in support adducing the experimental 

 result that while gum-like bodies are inactive, those of a more resinous 

 nature are active. The author, as the result of a number of experi- 

 ments, concludes that the activity is due not merely to resin or resin-like 

 bodies, but that tannin and tannin-like bodies, as well as some others, 

 may be responsible. It is at any rate clear that some body or bodies 

 in the liquefied cell-walls reduce silver-salts in the plate, and that these 

 bodies are either shot off, as if volatile, or diffuse readily, seems clear 

 from the want of sharpness in the microscopic details. 



* Bull. Torrey Bot. Club, xxxii. (1905) pp. 1-34 (17 figs.). 



t Naturwiss. Zeitschr. Land. Forstw., ii. (1904) p. 484-90. See also Ann. Mrcol.. 

 Hi. (1905) pp. 116-17. 



X Broc. Camb. Phil. Soc, xiii. (1905) p. 3-11. 



§ Phil Trans. Boy. Soc.,cxcvii. ser. B (1904) pp. 281-9. 



