252 



found most abundant in the stem and sometimes occurs to the extent of 

 30 per cent., as is often the case in the pine tree. It also varies greatly with 

 the age of the tree, and is frequently found as a coating on the bark. Halm- 

 Horstmar's investigations seem to indicate that silica is indispensable to 

 vegetation, but the later investigations of Sachs, Knop, Nobbe, Stiegert, 

 Wolff and others, indicate that it is not essential to the physiological de- 

 velopment of the plant. Its great abundance in the soil, however, accounts 

 for its occurrence in the ash of all trees. 



Lucanus' investigations show conclusively that the -oxide of manganese 

 is inessential to the development of the tree. 



It must be remembered that all the ash constituents which are neces- 

 sary to the growth of the tree may be absorbed by it in a much larger 

 quantity than is essential. 



The effect of an abundance of any one of the ash constituents of a tree upon 

 its vegetable products has been given some study, but no definite conclu- 

 sions have been reached. It is known, for example, that pears will flour- 

 ish on ground that would yield apples scarcely palatable, but the mineral 

 constituent wanting and necessary for the full development of the apple 

 is not known. 



Fruit growers agree that by the use of fertilizers you may affect the 

 growth of wood very much, but not the quality or quantity of fruit. The 

 best form to apply the mineral constituents to the soil is in the use of 

 stable manure which has the following average composition : Water 75 

 per cent, organic matter 19.2, ash 5.2, nitrogen .5, potash .63, soda .19, lime 

 .7, magnesia .18, phosphoric acid .26, sulphuric acid .16, silica .16, chlorine 

 and fluorine .19. 



The composition of the ash of trees certainly does not of itself afford suf- 

 ficient data to determine, with anything like certainty, which fertilizing 

 constituents or manuring mixtures should be applied to the various trees 

 in order to produce the largest yield of fruit. A knowledge of the composi- 

 tion of the ashes of trees, however, gives us warning that our trees will be- 

 come unhealthy if the soil on which they are grown is either wanting or 

 contains insufhcient quantities of one or more of the ash constituents neces- 

 sary for the growth of the tree. Often the amount of growth is sought to 

 be increased by the addition of ammonia when really the soil may be starv- 

 ing for mineral food. An excess of ammonia over the proper proportion 

 of mineral constituents does not enter into the growth of the tree, or in 

 other words, as before stated, the increase in growth in a tree is propor- 



