STATE POMOLOGICAL SOCIETY, 121 



to their activities. From its nature it increases the water hold- 

 ing capacity of the soil, which not only benefits the soil bacteria 

 but also is of the greatest importance to the trees when the dry 

 summer months come on and large demands are being made 

 upon the soil for water to develop the growing leaves, wood 



and fruit. 



So much for the cover crop— now wherein are the benefits of 

 cultivation? It is well known that a heavy soil is cold and 

 that the lighter and more porous it is the warmer it is. A soil 

 that is frequently stirred is better aerated. Frequent cultivation 

 tends to break up capillarity and consequently helps to prevent 

 losses of water from the soil by evaporation. Cultivation 

 also makes the particles of soil finer and thus allows more ready 

 access to the materials it contains. Hence we see that culti- 

 vation does much to produce the right conditions under which 

 these beneficial soil bacteria are able to do their work. 



The higher plants with green coloring matter, to which 

 class the apple tree belongs, differ from animals in that they 

 are able to build up from comparatively simple chemical com- 

 pounds, with the aid of this green coloring matter and the 

 energy obtained from sunlight, the quite complex food sub- 

 stances necessary for the repairing and building up of tissues 

 and the carrying on of various other vital processes within the 

 plant. Before we can intelligently discuss how the apple tree 

 does this and what bearing it has on a rational system of or- 

 chard management we must know something of the structure of 

 the various organs of the tree. 



All plants are built up of cells and these are of different kinds 

 and shapes and they are variously modified according to their 

 functions. The essential parts of a plant cell of the class to 

 which the apple tree belongs consist first of a cell wall made 

 up largely of a substance called cellulose which is readily per- 

 meable to water. It contains identically the same chemical sub- 

 stances and in the same proportions as starch but differs from 

 it in the way these substances are combined. Filter paper or 

 Taw cotton are almost pure cellulose. In woody tissues and 

 bark the cell walls have become much altered through the depo- 

 sition of other substances. Within the cell wall is the living sub- 

 stance called the cytoplasm or protoplasm. This is a nitroge- 

 nous or albuminous substance more closely resembling the 



