450 



THE POPULAR SCIENCE MONTHLY. 



Respiration of Plants. The leaf -respiration, so called, of plants 

 is not an excretory process, but rather a nutritive one. In effect it is 

 precisely the reverse of true respiration. It is a deoxidizing process 

 separating the components of carbonic acid under the influence of 

 the sun's rays, and depositing the carbon ; whereas respiration is an 

 oxidizing process the production of carbonic acid. However, during 

 germination and flowering, and in darkness, decomposition takes place 

 within the plant, resulting in the production and elimination of car- 

 bonic acid a true respiration. 



Many biologists now hold that there is a constant decomposition of 

 crude nutriment in the interior of plants, and therefore a slight respi- 

 ration, but that it is masked by the more prominent nutritive process. 

 The leaves are commonly, but wrongly, called the lungs of the plant, 

 for their chief function, as we observe, is not respiration, but nutrition. 

 It were more correct to regard them as the stomach of the plant. 



Fig. 3. Gills, a, J, c, or Annelida : d, of a Bivalve Mollusk. a, Navphanta celox (Greeff), 

 enlarged to three diameters, with broad gill-fins, b, foot, of Yanadis ornata (Greeff), with two 

 broad trill-fins, c, section of a segment of Eunice : br, the ramified gill-appendages of the ru- 

 dirneLtary foot. d. Mytilus edulis, with br, the gill-folds, and I, the lips separated from them. 



Organs of Respiration. As the function of respiration is so 

 simple in principle, being a single physical action, it can be conducted 

 almost anywhere in the body, or wherever the blood can be conven- 

 iently exposed to the surrounding medium. The nature of an animal, 

 as regards other less easily modified functions, and its peculiar circum- 



