368 ANNUAL EECORD OF SCIENCE AND INDUSTRY. 



assured. Applying these principles to certain well-known 

 plants, Kabsch finds for the grape-vine, for instance, that the 

 limiting temperatures between which the vine can be culti- 

 vated naturally are minus 19 C. and plus 20 C. The aver- 

 age degree of temperature must be plus 8 C. ; the sum total 

 throughout the year must be 2900. La Chaleur, Ghent, 

 1873,46. 



HEAT AND VEGETATION. 



Morren, of Liege, has presented his views on the relation 

 of heat to vegetation, especially as to the dynamic influence 

 of heat on the growth of plants. He says that we will elu- 

 cidate this matter slowly, in proportion as physics and chem- 

 istry make progress in the revelation of the nature of bodies 

 and forces. Heat has an influence upon the growth of plants, 

 on the circulation of the sap, elaboration of the cells, the res- 

 piration, and many other phenomena. The relation of heat 

 to the development of plants, and particularly the periodic 

 phases of vegetation, are phenomena known through the 

 epoch at which they manifest themselves, the mean dates of 

 these manifestations, and the average deviations therefrom. 



After giving an abstract of the results of the labors of 

 Schubeler, Hofmann, Fritsch, Linnsser, and Kabsch, Profess- 

 or Morren states that a problem of high importance, and 

 one which has been, perhaps, too much neglected, is that of 

 the relation between heat and the weight acquired by the 

 plant under the action of the solar rays, and especially its 

 relations to the quantity of carbon fixed in the organic mat- 

 ter, as far as we can at present estimate that. In a temper- 

 ate climate a hectare of forest and prairie, or cultivated land, 

 fixes in one year from 1500 to 6000 kilogrammes of carbon; 

 and in order to accomplish this work vegetable organisms 

 utilize between one and four thousandths of the heat which 

 has been received by solar radiation upon the surface that 

 they occupied. It is evident that such phenomena as take 

 place periodically, viz., germination, leafing, etc., are acts of 

 growth ; such growth supposes movement ; the fact of the 

 movement necessitates consumption of force, which consumj> 

 tion is but a transformation of heat. If, to fix our ideas, we 

 suppose an apple to fall from a tree, we have but to reflect 

 upon the laws of force in order to see that the apple must 



