SOCIETIES 



299 



there definite communities exist, made up of groups of the same 

 kind of plants, while certain animals will be found living on the 

 plants or among them. Evidently conditions of food and shelter 

 are responsible for this close association. We can see that each 

 one of these plant groups in the community evidently came 

 originally from a single individual which flourished under the 

 peculiar conditions of soil, water, light, etc., that were found in 

 this spot. These single plants have evidently given rise to like 

 plants which made up a family group, and thus have popu- 

 lated the locality. This is often seen in a pine grove, or in an 



Wright Pierce 

 A plant society. Can you name the various plants that are living together in this group? 

 What conditions and adaptations make it possible for them to live together in one society? 



area covered almost exclusively with ferns. Later, seeds of other 



plants may be carried there by the wind, birds, or other animals, 

 I and we find widely different plants living under similar conditions. 

 I They all need the same substances from the air, the water, and the 



soil. They all need sunlight ; they use the same food. Therefore 



there must be competition among them, especially between those 

 s near to each other. The plants which are strongest and best 



fitted to get what they need from their surroundings, live ; the 



weaker ones are crowded out and die. 

 But their lives are not all competition. The dead plants and 



animals give nitrogenous material to the living ones, from which 

 | the latter make living matter ; some bacteria provide certain of 

 \ the green plants with nitrogen; many of the green plants make 



