AGRICULTURAL BOTANY. 27 



tions in Australia to clot ermine the rate of transpiration under Australian con- 

 ditions, tlie rate of ascent of sap. especially in eucalyptus trees, the condition 

 of conducting tissue during active transiiiration. and the resistance to flow 

 in stems. 



It was found that the rate of evaporation per square meter of leaf surface 

 from (ut branches, whether placed iu water or not, is always less than from a 

 plant rooted in the soil. When the air is hot and dry the evaporation from a 

 fre<> surface of water undergoes an enormous increase, but from a living plant 

 it undergoes a regulatory decrease, in which case it may become only one-sixth 

 as much as from a free water surface. Cut trees were found to absorb water 

 at a less rate than rooted ones evaporated it. The maximum rate of ascent of 

 sjip noted was 12.3 meters per hour in Eucalyptus vitninaUs. In cut branches 

 of other species of Eucalyptus and in cut acacia trees it rarely exceeds 1 to 2 

 meters and is often less than 1 meter per hour. Branches containing air and 

 taken from transi)iring trees showed a much greater resistance to flow than 

 when saturated with water. To produce the transi)iration rate of flow a head 

 of water 2 to 10 times the length of the stem may be required, but in fully satu- 

 rated stems with large long vessels a head of one-tifth the length of the stem 

 may be sufficient. 



An experiment showed that a colored liquid would rise slowly in a saturated 

 stem kept in a saturated atmosphere, but somewhat more slowly if the stem 

 was killed, indicating that the phenomenon is not the result of any vital pump- 

 ing action that is not capable of a physical explanation. 



No appreciable rise of sai) was found to take place in trees deprived of their 

 leaves, a pumping action being excited only when the leaves are exerting suction 

 on the water in the wood. 



Influence of light on the expanding' of the buds of woody plants, W. Lubi- 

 MENKO (Izv. Imp. Akad. Nauk (Bui. Acad. Imp. Sci. St. Pctersb.), 6. scr.. 1910, 

 No. 2, pp. 163-168).— In a previous publication (E. S. R., 20, p. 1124) the author 

 showed that the intramolecular nutrition of plants, independent of photosyn- 

 thesis, is regulated by the amount of illumination received. His previous ex- 

 periments have been extended to include the effect of light on the opening of 

 buds. Branches of lilac, beech, linden, white birch, and oak were placed under 

 bell jars, and by means of various layers of paper the illumination was regu- 

 latetl or reduceil. 



Light was found to stimulate the development of buds aftei; their winter 

 rest even when the illumination was reduced to such an extent that it could 

 not have any photosynthetic power. In the case of lilac and beech there seemed 

 to be an optimum of light, after which the development was retarded. The 

 expansion of the linden, birch, and oak buds took place very slowly in reduced 

 liglit. these species demanding a considerable amount of light for their 

 development. 



It is claimed that the experiment shows that the buds of woody plants require 

 a period of preparation before their expansion and that during this i)eriod a 

 certain amount of light is necessary. When this preparatory period has passed 

 the buds expand in darkness or light. It is held, therefore, that light exerts an 

 indirect influence' on the growth of l»uds. 



The action of ultraviolet light on plants, M. Cercelet (Rev. Vit., S3 (1910), 

 No. .S-JJ, pp. t2.'i-hi9). — A n'sume is given of various investigations which show 

 the action of the ultraviolet light \\\)o\\ the growth and develojiment of plants. 



On the increased growth of persistent leaves, D. De PEmiOLA (Ann. Hot. 

 [Uontc\. 7 (1909), No. .3, pp. 321-330, pi. I; abx. in Bot. Vcnthl., 113 (1910), 

 No. .5, p. 115).— A brief account is given of the author's iuvestigatious ou the 

 increase in thickness of persistent leaves. 



