ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 197 



of the area controlled. The author believes that the streaming is due 

 to pressure and suction produced by dilatations and contractions of a 

 slow, rhythmic respiration. 



Physiology of the Cells of Spirogyra.*— C. van Wisselingh has 

 studied the physiology of Spirogyra, and finds that the influence of the 

 nucleus starts before karyokinesis, when it determines the position 

 where cross-wall formation shall take place. Starch-absorption is de- 

 pendent upon certain chemical changes brought about under nuclear 

 influence. Cell- walls are formed by the action of the nucleus in con- 

 verting starch into materials suitable for wall-formation. The nucleus 

 also exerts an indirect influence upon turgidity. The chromatophores 

 appear to have a certain individuality apart from the nucleus, for small 

 pieces can grow and form pyrenoids in cells which have no nuclei. 

 Starch-formation in the chromatophores is not directly influenced by 

 the nucleus. The plasma is able to increase in cells which have no 

 nucleus. Movements of the plasma are not directly weakened by the 

 absence of the nucleus, and the plasma of those cells which are without 

 a nucleus streams much more quickly than in normal cells. 



Irritability. 



Influence of Light on Fruit-development.t— W. Lubimenko has 

 studied the effect of light in promoting the development of fruit, and 

 finds that it is only during the first stage of fruit-development that 

 light is absolutely essential ; subsequent to this period the fruits will 

 develop equally well in darkness. The experiments show, however, 

 that fruits ripening in darkness have fewer seeds than those growing in 

 light ; also that the dry weight of such fruits is less. A few experi- 

 ments made upon Primus Cerasus, Vitis vinifera, and Sorbus Amuparia 

 show that the acidity of the fruits developed in partial daylight is 

 usually much less than that of fruits ripened in the open air. Thus 

 light appears to be an important factor in fruit-development. 



Effect of Light upon the Colour of Algae 4— G-. A. Nadson gives 

 the result of his experiments upon the effect of the intensity of light 

 upon the colouring of algse. The blue-green Phormidium laminosum 

 grows in shady places. A specimen placed in a window facing east, so 

 as to catch some sunshine daily, assumed in two months time a bright 

 golden-yellow colour. In autumn, as the sunshine weakened, the blue- 

 green colour partly returned. Similarly a yellowed specimen, after re- 

 moval to a shaded position, regained in about four months its typical 

 blue-green colour. Oscillaria amphibia behaves in the same way. 

 Some of the Rhodophycese— Porphyra laciniata, Nemalion lubricum, 

 Laurencia obtusa — in bright sunshine assume a brownish -yellow or 

 golden-brown colour. In Phormidium the amount of chlorophyll 

 diminishes in bright sunshine and the yellow colouring matter (lipo- 

 chrome) becomes the more evident. The colour changes can be ranged 

 in three categories :— (1) the fading and change to a pale yellow ; 



* Bot. Centralbl., xxiv. (1908) pp. 133-210 (3 pis.). 



f Comptes Rendus, cxlvii. (1908) pp. 1326-8. 



% Bull. Jard. Imper. Bot. St. Petersbourg, viii. (1908) pp. 122-13 (pi.). 



