82 THE POPULAR SCIENCE MONTHLY. 



cal integration. The organisms which subsist upon it are functionally- 

 low, the forces which might have been otherwise employed being used 

 up in the formation of protoplasm and other high organic compounds. 



The conditions of alimentation limit the vegetable world to one 

 general form. Plants do not need to seek food ; food seeks them. 

 Thus no motive powers are requisite, and they remain fixed in one 

 position. But food seeks them in two different localities, the earth 

 and the air. The earth constituent comes to them dissolved in water, 

 the atmospheric constituent dissolved in air. They must, therefore, 

 have powers of extension sufficient to occujDy both these fields. This 

 power is obtained by growth, root-extension seeking the liquid food, 

 leaf-extension the gaseous food. 



These general conditions confine plants to one generic form, a 

 connecting link of stem between earth and air, and an extension of 

 root-mouths into the soil and of leaf -mouths into the atmosphere. A 

 tree is a society, or family ; the main stem being the patriarch of the 

 flock, the earth and air branches its descendants, and the leaves and 

 rootlets its latest unisexual offspring. 



As the type of animal form is the stomach, so the type of plant 

 form is the mouth. It has not yet developed into the formation 

 of a central stomach, nor has it attained powers of digestion. It 

 builds up protoplasm by successive steps of chemical integration. It 

 is a laboratory for the production of chemical synthesis not of 

 chemical analysis, as in animals. 



Thus the food-taking requisite is provided for in the production of 

 numerous leaf and root mouths, extending themselves into the two 

 great reservoirs of food. But defense must be provided for as well. 

 Plants are attacked by various foes. Fierce storms assail them. These 

 can only be resisted by an inmate strength or elasticity. Wintry cold 

 congeals their food-supply. They must therefore be capable of hiber- 

 nating. Animals seek to devour them. They can only escape by 

 inclosing themselves in a rigid armor, or by becoming unfitted for 

 animal food. 



This leads us to the most significant adaptation in plants. Their 

 life duration is limited, and they must have powers of reproduction, 

 the best adapted in this respect crowding out the less adapted. Obvi- 

 ously the seed-bearers are best fitted for survival ; and of these, those 

 bearing the most seeds, and having the best facilities for dispersing 

 them. 



But the fixed plant can not, of itself, spread its seeds beyond its 

 own locality. It must be aided by other agencies. Many plants 

 avail themselves of air-currents for this purpose, the seeds being pro- 

 vided with curious appendages to aid them in flying or rolling before 

 the winds. In other cases the seed is surrounded by a store of pala- 

 table food, offering an inducement to the higher animals to devour it, 

 and thus to disseminate the seeds. 



