442 SUMMARY OF CUEREXT RESEARCHES RELATING TO 



largely controls transpiration, a fact neglected by Ewart. Moreover, 

 the resistance appears to have been over-estimated, owing to insufficient 

 care in prevention of air bubbles and clogging at the cut surface. The 

 author maintains that even under the most favourable conditions for 

 transpiration, and with an equal velocity throughout the tree, a head of 

 water of the same height as the tree would be sufficient to maintain the 

 current. Thus, he concludes that Ewart's objections to the cohesion 

 theory are ill-founded, and that this theory is likely to be correct. 



Anaerobic Respiration.* — J. Stoklasa, A. Ernest, K. Chocensky have 

 investigated the anaerobic respiration of seed-plants, and have come to 

 conclusion that it is of the nature of an alcoholic fermentation. The 

 experiments were performed upon such plants as the beet and the potato, 

 and various portions of the plant were used. e.g. foliage-leaves, roots, 

 tubers, etc. Similar results were obtained both with frozen and normal 

 material. The foliage of the beet gave off 166-1 mg. in ninety-six 

 hours, while the root gave off 81 "5 mg. (calculated for 100 grm. of 

 fresh material). 



Respiration of Aerial Vegetative Organs.f — G. Nicolas has experi- 

 mented upon twenty different species belonging to different orders, with 

 special reference to respiration of aerial organs of vascular plants. His 

 results show that each of the aerial organs has its own intensity and 

 respiratory quotient, those of the stem and petiole being most nearly 

 alike. Those organs which are especially concerned with assimilation, 

 i.e. leaves, plyllodes and cladodes, have the greatest respiratory intensity 

 and the lowest respiratory quotient. 



Irritability- 

 Light Reactions in Volvox.J — S. 0. Mast has studied the effects of 

 light upon Volvox. The eye-spots are on the outer posterior surface of 

 the individuals, being much larger on those forming the anterior end of 

 the colony, and probably acting as light recipients. The rotation is 

 usually anti-clockwise, and when swimming horizontally the colony 

 seldom moves parallel with the Hght rays, the colonies with large 

 daughter colonies or spores showing most deviation. The specific 

 gravity of the colony is less than one, so that when at rest, it sinks. 

 Volvox tends to swim in the direction of its longitudinal axis, but 

 gravitation causes the axis to become vertical. The colony orients so as 

 to assume a given angle to the rays of light, and if exposed to two lights 

 of equal intensity, it swims in a middle position. The direction of 

 motion is regulated by the light intensity upon each side of the colony, 

 and is due to motor reactions of the individuals in the colony. Move- 

 ment is dependent upon the physiological condition, and the time of 

 exposure and intensity of light ; it cannot be induced by mechanical 

 stimulation or change in temperature. Weber's law is approximately 

 correct for the light reactions of Volvox. 



* Ber. Deutsch. Bot. Gesell., xxiv. (1906) pp. 542-52. 



t Comptes Rendus, cxliv. (1907) pp. 1128-30. 



X Journ. Comp. Neurol, and Psychol., xvii. (1907) pp. 99-180 (15 figs.). 



