NUTRITION 81 



from ammonia by the nitrite bacteria, and the sulphur 

 bacteria can live only where sulphuretted hydrogen is abun- 

 dantly set free either by organisms or in sulphur springs, so 

 in the humus soils some organisms live upon the simpler 

 products of their neighbors. It is easy to conceive that more 

 than neighborhood nearness might be advantageous to some, 

 and that these, gradually growing together, might form 

 associations, mutually though perhaps not equally benefi- 

 cial. The penetration of small organisms, or small parts of 

 organisms, into and even through the living cells of others, 

 is not necessarily fatal to the penetrated cells, as is shown 

 by the symbiotic association of algae enclosed in the cells 

 of certain Infusoria, and even by some parasitic associa- 

 tions. * 



In all of these cases, however, we have no new physio- 

 logical principles. The nutrition is fundamentally the same, 

 the food-materials are acquired and elaborated, the foods 

 are assimilated and incorporated, in the same way in all 

 organisms, although the sources of food may be different in 

 different cases. 



CARNIVOROUS PLANTS 



The carnivorous plants have been exploited especially 

 by "ecologists," students of the adaptations of plants to 

 their surroundings, and their writings furnish the proper 

 sources for more general information regarding them ;t but 

 the peculiarities of their nutrition are still within the prov- 

 ince of pure physiology. These extraordinary plants may 

 be divided into two classes: first, those which forcibly 

 capture, and second, those which simply entrap, their prey. 

 These classes may be represented respectively by Dion&a, 



* For example, the cases cited by De Bary (Morphology and Biology of 

 the Fungi, Mycetozoa, and Bacteria, Eng. transl., p. 392, 3) and the sur- 

 vival of chlorophyll-containing cells of the host even when penetrated 

 by cells from the haustoria of Cuscuta (Peirce, Annals of Botany, Vol. 

 vii., p. 308, 1893). 



\ See Darwin's Insectivorous Plants, Goebel's Pflanzenbiologische Schil- 

 derungen (Insektivoren), Kerner and Oliver's Natural History of Plants 



((Vol. I., part I.), Cohn's Die Pflanze (Bd. II., Insektenfressende Pflanzen), 

 Ludwig's Lehrbuch der Biologic der Pflanzen, etc., etc. 





