Physiologie. 185 



Hasselbring, H., The effect of shading on the transpira- 

 tion and assimilation of the tobacco plant in Cuba. 

 (Botanical Gazette. LVII. p. 257-286. 1914.) 



Under the climalic conditions of Western Cuba, where the 

 writer made his researches, the transpiration of tobacco plants 

 grown in the open ground is found to be nearly 30 per cent greater 

 than the transpiration of plants grown under the cheese-cloth shade 

 commonly used for shading tobacco in that region. The transpira- 

 tion per Unit area of leaf surface is nearly twice as great in the 

 sun plants as in shade plants. 



The shading of tobacco plants b}' this grade of cheese-cloth 

 does not seem to result in a diminished production of total plant 

 substance by the shaded plants as compared with other like plants 

 not shaded. Since, however, the leaves of the shade-grown plants 

 have a rauch greater total area than those of plants grown in the 

 open, it is evident that the quantity of plant material elaborated 

 per Unit of leaf area is greater in the plants grown in the open. 



Although the total production of dry plant substance is not 

 influenced in any marked degree by the cheese-cloth shade, the 

 distribution of this substance is affected in such a manner that in 

 the shade-grown plants relatively less material is deposited in the 

 leaves and more in the stems than in the corresponding organs of 

 the plants grown in füll light. No evident influence is exerted on 

 the disposition of material in the roots. M. J. Sirks (Haarlem). 



Hoy t, W. D., Some effects ofcolloidal metalson Spirogyra . 

 (Botanical Gazette. LVII. p. 193—212. 1914.) 



The researches, published in this paper, are summarized by 

 the writer as follows: 



CoUoidal silver was fatal to filaments of Spirogyra in all con- 

 centrations above 0.045 ppm. and was injuriousas low as 0.00225 ppm. 

 The weaker Solutions of silver were rendered almost or entirely 

 non-toxic, during the period of the experiments, by addition of col- 

 loidal platinum, animal charcoal, or inorganic salts, to form a 0.5 

 per cent Crone's Solution. 



A Solution containing 90 ppm. of coUoidal gold and approxi- 

 mately 0.02 per cent of NaOH was only very slightly injurious. 



A Solution containing 96 ppm. of coUoidal platinum was almost 

 non-injurious during the period of the experiments, and, in less 

 concentrated Solutions, partially corrected the toxity of tap water, 

 ordinar^'-distilled water, and Solutions ofKCl, MgS04 and coUoidal silver. 



CoUoidal gold, coUoidal platinum, and, to a less extent, col- 

 loidal silver, in low concentration, all partially prevented injury to 

 the alga filaments by toxic Solutions of NaOH. Addition of AuClo, 

 to a toxic Solution of NaOH, or of PtCl4 to a toxic Solution of MgSÖ4 

 did not render the hydrate Solutions less toxic. 



VVhen Spirogyra was placed in a Solution containing coUoidal 

 platinum or coUoidal gold together with NaOH, the outer portions 

 ot the cell walls swelled, forming crumpled, gelatinous sheaths, 

 which became deepty stained by the metal. This swelling was espe- 

 cially pronounced when the filaments v/ere transferred from the 

 alkaline coUoidal gold or platinum Solution to nontoxic distilled 

 water. The swollen masses thus produced ofien parted from the 

 rest of the wall, leaving the latter uncolored and apparently un- 

 affected. 



