600 SUMMARY OF CURRENT RESEARCHES RELATING TO 



liquid containing a large number of zoospores be raised to a temperature 

 of 40° C, all movement stops and is never afterwards renewed. The 

 zoospores are, however, not killed, for after a certain time thej divide ; 

 this shows that at about 40^ C. the cilia are destroyed. Zoospores, 

 which are arrested hj a sudden rise of temperature, are able to renew 

 their movement. 



Reactions of Chlamydomonas to Physical Agents.*— P. Desroche 

 describes his experiments on Chlamydomonas ohtusa Braun. He comes 

 to the conclusion that a definite organism reacts to exterior agents with 

 as much precision as inert matter. Two factors must be taken into 

 account : the physical or chemical agents, and the organism itself. He 

 establishes the following facts : (1) white light orientates the zoospores, 

 but does not influence the speed of their movements, however intense. 

 A too intense light arrests their movement. 2. Visible radiations of 

 the solar spectrum have different influences on the movement of zoo- 

 spores : the effect of each is described. 3. Temperature acts on the 

 movement of zoospores, a sudden variation arresting it. Within the 

 limits between which movement is possible, speed increases with the 

 temperature. Above 40° movement is arrested. Freezing-point does 

 not kill the zoospores. That is only attained at a temperature between 

 - lb° and - 19". Theories for this are discussed. 4. The apparent 

 negative geotropism of zoospores may be reduced to a simple mechanical 

 phenomenon. 5. Variations of pressure, within the limits w^hich have 

 been tested, appear to have no influence on zoospores. The author 

 concludes finally that, as regards reactions which affect movement, 

 physical agents appear to act simply in provoking or arresting it, 

 without modifying its nature or influencing its speed. The physiology 

 of the zoospore is only affected by very low or very high temperatures. 



Study of Saprophytic Algae. f — S. Mendrecka gives an accouni: of 

 her experiments in the cultivation of Chlorella variegata and other low 

 alg^ upon various media, and of the effect of the latter upon the 

 growth and colour of the algae. C. variegata grows best on peptone 

 and sugar solution, and fairly well on solutions of ammoniacal salts. 

 The effect of light or darkness is not of much importance. What is of 

 importance is that sugars, especially glycose and galactose, can afford 

 complete nutrition for the plant and bring it to the state of sapro- 

 phytism, depriving it of its green colour. Certain salts also more or 

 less decolorize it. On the other hand, peptone maintains the chlorophyll 

 colour of the plant even in darkness, and restores the green colour to a 

 cultui'e which was colourless at the start. 



Differentiation of Algse by Agglutinin. { — S. Rosenblatt-Lichten- 

 stein describes her experiments on the differentiation of algai by means 

 of specific agglutinin. Such work is almost a new line in algae. The 



* These de Doctorat es-Sci.-nat. Paris: (1912) 160 pp. (31 figs.). See also 

 Bot. Centralbl., cxxiii. (1913) p. 7. 



t Bull. Soc. Bot. Geneve, v. (1913) pp. 150-80 (figs.). 



X Arch. Anat. Physiol., Physiol. Abt. (1912) 415 pp. See also Bot. Centralbl., 

 cxxiii. (1913) p. 64. 



