Physiologie. 107 



Dixon, H. H., Vitality and the transmission of water 

 through the stems of plant s. (Scient. Proc. Roy. Dublin 

 Soc. XII. p. 21—34. 1910.) 



The author argues that if there is any sort of vital action which 

 even facilitates the passage of water upwards, its effect would be 

 observable experimentally by a downward filtration of water more 

 rapid in a killed than in a living stem. Hence he arranged two 

 similar shoots of Syringa vulgaris in order to determine the amount 

 of water that would pass downwards through them, both being 

 alive, under a given head of pressure in a short time. One shoot 

 was then killed, by steam or poison, and the amount of water trans- 

 mitted by both was again determined. No appreciable or constant 

 difference was found, hence the author concludes that the living 

 cells of the wood do not influenae the rate at which water is 

 transmitted through the stem. F. Cavers. 



Ewart, A. J. and B. Rees. Transpiration and ascent of 

 water in trees under Australian conditions. (Ann. Bot. 

 XXIV. p. 85—105. 1910.) 



The authors have carried out experiments similar to those 

 already described by Ewart, with the object of comparing Austra- 

 lian material and climatic conditions with those of England. Most 

 of the experiments were made with species of Eucalyptus, on the 

 heights of which some details are given; some of these trees may 

 reach HO m. It was found that transpiration from severed branches 

 was always distinctly lower than that from intact trees; m experi- 

 ments lasting for several hours during which there was a conside- 

 rable rise in air temperature, transpiration increased much less 

 rapidly than did evaporation from a free water surface and even 

 feil off, indicating self-regulation. The maximum transpiration in 

 Eucalyptus spp. was extremely high — in E. corynocalyx, for in- 

 stance, nearly 400 g. water per sq. cm. of leaf area, as compared 

 with 17 g. in Dracaena Draco. The rate of flow of the transpiration 

 current was found to be very great, 6—12 m. per hour in some 

 Eucalyptus spp.; measurements by means of mercury injection 

 showed the lenght of the vessels in the stem of Eucalyptus and 

 Acacia spp. to be several m., the vessels in the branches being 

 shorter and narrower, F. Cavers. 



Irving, A. A., The beginning ofphotosynthesis and the 

 development of ch loroph vll. (Ann. Bot. XXIV. p. 805—818. 

 1910.) 



The author finds that seedlings grown in darkness and then 

 transferred to light, or grow:n from the first in light, are able to 

 fix all the COo produced by respiration only after they have become 

 almost fully green. Up to this stage, the photosynthetic activity 

 never fixes tnore than 10% of the CO.^ of respiration, and never 

 amounts to more than 1^/^ of the activity after the füll development 

 of the Chlorophyll. The author concludes that the first development 

 of the photosynthetic function bears no relation to the amount of 

 Chlorophyll produced; that the amount of Chlorophyll present is 

 never a limiting factor to assimilation in these early stages of the 

 assimilating organs; that the beginning of complete functional acti- 

 vity must be controlled by some other component part of the pho- 



