SOCIAL DISJUNCTIVE SYMBIOSIS 



57 



of labor among the individuals of a human comnnmity, some being 

 engaged in sn])plying food, others in sui)i)lying clothing or fuel, 

 others in administering the law, etc. In the plant community there 

 is a somewhat comi)arable division of labor among the various 

 species, though not among the individuals of the same species. The 

 function in the community of all individuals of the same species is 

 the same, but some species have the function of manufacturing food, 

 some of supplying a ground cover to check evaporation of water from 

 the soil, some to act as scavengers in getting rid of dead bodies 

 (Fig. 21), etc. One important difference between the human com- 

 munity and the plant community, however, must be kept in mind. 



Fig. 21. — Polyporus giganteus hastening the decay of a stump. 



In the human community there are ordinarily more or less definitely 

 organized activities carried on for the good of the community as a 

 whole. In the plant community, on the other hand, there is no 

 altruism. It is a case of every plant for itself. The activities of 

 certain species do result advantageously for the community as a 

 whole, but this is due to chance circumstances, and the activities 

 would be carried on just as vigorously if they were resulting in harm 

 to the community. This fundamental difference betw^een the two 

 communities, however, is the natural result of the presence of con- 

 sciousness in the human species and the lack of it in plants, and as 

 soon as we leave that fact out of consideration the two types of com- 

 munities become strikingly similar. 



Species in a plant community that are very different are often 

 incidentally of very great service to one another. The trees, for 



