Physiologie. 129 



The most reliable results are obtained by the use of uniform 

 material and by taking for measurement only such parts as come 

 into iramediate contact with the Solution. M. J. Sirks (Haarlem). 



Otis, C. H., The transpiration ofemersed water plants: 

 its measurement and its relationships. (Bot. Gazette. 

 LVIII. p. 457-493. 1914.) 



The writer summarizes his paper as foUovvs: 



Emersed water plants transpire large amounts of water. 



With one exception (water lily), the evaporation taking place 

 from a water surface occupied by emersed water plants is much 

 greater than that which takes place from a free water surface of 

 the same area and subjected to the sarae external conditions. 



The amount of evaporation from a water surface on which 

 water lilies are growing is less than that which takes place from 

 a free water surface of the same area and subjected to the same 

 external conditions. 



The amount of evaporation from a water surface occupied by 

 emersed water plants depends upon the following factors: (a) the 

 species of plants; (b) the density of plant stand; (c) the amount of 

 plant surface exposed to the evaporating power of the air; (d) the 

 height of the plant growth above the level of water; (e) external 

 factors (physical factors, like wind, temperature, relative humidity, 

 etc.); (f) internal factors (chemical and physiological phenomena 

 within the plant). 



Transpiration from emersed water plant surfaces occurs both 

 by day and by might, but transpiration by day is greatly in excess 

 of that by night. 



For diflferent species there is no constant ratio between rate of 

 transpiration and the area of surface exposed. 



The rate of evaporation from the transpiring surface of an 

 emersed water plant during the day may equal, and in some cases 

 may exceed that from a free water surface of the same area; but 

 at night the evaporation from a free water surface is usually greatly 

 in excess ot that from a transpiring plant surface. 



Wind, temperature, and relative humidity undoubtedly have 

 a great influence on the rate of transpiration of emersed water 

 plants, but these factors alone do not explain the great difference 

 existing between transpiration of emersed water plants and the 

 evaporation from a free water surface. 



These data are of economic importance in indicating what 

 plants should be grown in and what plants should be excluded 

 from storage reservoirs in regions of small rainfall and scant water 

 supply. M. J. Sirks (Haarlem). 



Roux, W., Die Selbstregulation, ein charakteristisches 

 und nicht notwendig vitalistisches Vermögen aller 

 Lebewesen. (Nova Acta. Abh. Kais. Leop.-Karol. deutsch. Ak. 

 Naturf. C. 2. 91 pp. 1914.) 



Die Vitalisten glauben die physische Organisation der Lebewe- 

 sen nur auf solche Weise erklären zu können, dass sie ausser den 

 physischen: typischen und regulatorischen Gestaltungsleistungen 

 ein metaphysisches gestaltendes Agens, eine Gestaltungsseele, be- 

 hufs Determination des Geschehens annehmen. Für sie besteht 



Botan.Oentralblatt. Band 181. 1916, 9 



