ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 221 



The primary action of the rays of the sun on vegetation consists 

 in thermic and photo-chemical effects, the influence of which on the 

 separate constituents of the cells is directly recognizable in intense 

 light. The photo-chemical effects relate exclusively to the behaviour 

 of the plant towards the oxygen and carbonic acid of the atmosphere ; 

 they are simply changes of intensity in the interchange of gases. 

 These have been fully determined in the absorption of oxygen, less 

 completely in that of carbonic acid. It cannot be then that light 

 produces any other effect on the plant than the thermic and the 

 photo-chemical. 



All the action of light on the phenomena of vegetable life, not 

 merely on growth and metastasis, but also the so-called mechanical 

 and vital movements of irritation caused by light, can readily be 

 traced to purely thermic and photo-chemical effects. A more exact 

 knowledge of them requires, however, a special investigation of the 

 behaviour of those constituents of the cell which are sensitive to light, 

 i. e. which are photo-chemically excitable. For an investigation of 

 them, and of their differences from those constituents which are not 

 excitable photo-chemically, the reader is referred to the author's 

 treatises on the functions of chlorophyll and the action of light 

 upon it.* 



Production of Heat by Intramolecular Respiration. f — Dr. J. 



Eriksson has made a series of observations for the purpose of deter- 

 mining the amount of heat, and the length of time for which it lasts, 

 caused by the intramolecular respiration of plants. The experiments 

 were made with the inflorescence of Aroide^, the flowers of other 

 plants, ripe fruits, germinating seeds, and yeast-cells, care being taken 

 to exclude the access of atmospheric oxygen. In most cases the eleva- 

 tion of temperature under these circumstances did not exceed • 2° C, 

 while access of air caused a rise of about 1°. With seedlings of lentil 

 the elevation of temperature continued for six days ; with buckwheat 

 for two days. In the case of fermenting yeast, however, an elevation 

 of 3 • 9° was observed, which was not increased by the subsequent 

 letting in of a stream of air. Yeast not in a state of fermentation 

 showed only the slight rise of temperature common to other plants. 



Physiological Functions of Transpiration. J — F. Eeinitzer pro- 

 pounds the theory that transpiration is an injurious agent, a necessary 

 evil, in the life of the plant. This view he founds on the fact that 

 transpiration exercises a retarding influence on growth. He regards 

 woody tissue as the cause of rapid movements of water in the plant, 

 rather than as being — according to Sachs's view — formed as the result 

 of such movements. 



Metastasis. § — The first volume of Pfeffer's ' Handbook of 

 Metastasis and Metacrasis' (Stoffwechsel u. Kraftwechsel) is occupied 



* See this Journal, iii. (1S80) pp. 117, 4S0 ; i. (1881) p. 479. 

 t Unters. aus dem bot. Inst. Tubingen, i. (1881). See Bot. Ztg, xxxix 

 (1881) p. 597. 



% SB. Akad. Wiss. Wien, Ixxxiii. (1881) pp. 11-36. 



§ W. Pfeffer, ' Stoffwechsel,' 38.3 i)p. (39 figs.). Leipzig,18Sl. 



