370 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



cured. This heat in the dark is especially favorable to an 

 active respiration, as we find that the quantity of carbonic 

 acid increases in proportion to the increase of temperature 

 in the leaf, so that there seems to be a relation between the 

 rapidity of growth and. the energy of respiration. 



This can easily be appreciated when we assume that a 

 certain portion of the heat must enter into action in order 

 to the formation of the immediate principles. The internal 

 combustion, which is indicated by the absorption of oxygen 

 and the throwing off of carbonic acid, is probably the source 

 of the heat necessary for the formation of the new immedi- 

 ate constituents. 19 C^June 20, 1874, 235. 



IODINE AND BROMINE IN FRESH-WATER PLANTS. 



Zen o-er states that Petter detected iodine in the ash of 

 the Cladophora glomerata in 1862, and that Jessler subse- 

 quently determined the amount to be 0.2343 grains in 9960 

 grains of the dried alga3. According to his own analyses, 

 the ash of the plant amounts to 52.85 per cent., and 56,000 

 grains of ash contain 21.5 grains of iodine and 8.5 grains of 

 bromine. The large amount of ash consists mainly of lime. 

 He concludes from his own experience that iodine and bro- 

 mine are present in much larger quantity than is suspected 

 in fresh -water plants, and that they are also present in 

 land plants, and suggests that fresh-water plants, by reason 

 of their wide distribution, may become an important source 

 of these elements. His most recent investigations of the 

 aquatic plant Lemna minor show the presence of a large 

 amount of iodine, and also of bromine. 18 C, April 14, 1875, 

 229. 



ORGANIC SUBSTANCE IN THE PLANT. 



A resume of the past progress and present condition of 

 our knowledge of the production of organic substance in the 

 plant is given, in the Prussian LandwirthscJiaftlicJie Jahr- 

 biccher, by Professor Pfeffer, of the University at Bonn. Pro- 

 fessor Pfeffer concludes that the production of organic sub- 

 stance from inorganic materials is dependent upon the ac- 

 tion of chlorophyl, and requires in connection with the col- 

 oring matter of the latter nitrogenous protoplasm. The 

 first product is generally starch, occasionally sugar, still less 



