96 COMPOUND ORGANS OF PLANTS. 



and the fertile valley, the sandy soil and the marshy swamp, 

 the margin of rivers and shores of the ocean, have all their 

 peculiar species of plants. The chemical composition of the 

 ash of a plant being known, scientific conclusions can be drawn 

 as to the soil most suitable for its growth. 



A good soil must contain all the substances fomnd in the ash 

 of the plant. This is a matter of great importance to the agri- 

 culturist. If we give abundant and vigorous food to an animal 

 it becomes strong and fat ; if its food be small in quantity and 

 poor in quality, it becomes poor and lean. Just the same 

 happens to a plant. Plants will grow vigorously and fruit 

 plentifully when there is an abundance of that kind of food in 

 the soil which is the most suited to their organization; and 

 their growth will be checked and their fruit injured by any 

 deficiency in their proper food. Nature is a wise and perfect 

 cultivator. Some plants are found in a moist soil, others in a 

 dry one. Some seek the cool shade, others the warm sunshine; 

 some are natives of lofty and barren mountains, others of lowly 

 and fertile valleys ; some fixed to rocks delight in the noisy 

 waves of the sea ; others attached to stones in brooks and 

 rivers grow beautifully in their quiet waters. All plants, how- 

 ever, are placed by nature in soils which are chemically and 

 physically adapted to promote their growth, so that they may 

 answer her grand and secret purposes in the development of 

 their organization. 



The motion of the sap in plants. — The function of nutrition, 

 which in the higher animals comprises a variety of distinct 

 processes, is reduced in plants to the utmost degree of simpli- 

 city. When water charged with nutritive substances from the 

 soil enters the cellular extremities of the roots, it immediately 

 fills the cells and vessels of the plant, and becoming subjected 



