SOILS. 200 



foothold in the city, at least for the present or as long as the vigilance is 

 continued, since the hand picking of these bags is the standard means of 

 fighting the pest as it occurs on deciduous trees even in the eastern cities 

 where it has become necessary to fight it. Every bag destroyed means 

 several hundred or more caterpillars less next summer. The other con- 

 trol measure is spraying the trees with arsenical poisons at the hatching 

 time of the eggs, especially on the evergreens, where the hand picking 

 is more difficult and the injury more severe, but this involves considerable 

 expense and labor and could well be avoided." 



SOILS. 



Paper Read by Alfred Burton Before the Florists' Club of Philadelphia, 



April 2, 1912. 



What is soil? Soil is the home of the roots of the plant. Soil is the 

 storehouse for that part of the food which the plant takes in through its 

 roots. Soil is the laboratory or kitchen where the food is prepared. And 

 this work goes on unceasingly. Lastly, soil is a support to hold the plant 

 firmly in its place. 



But what is soil? Soil is finely divided rock as can be readily -eeen 

 with a microscope, clay being the finest and sand and gravel the coarsest 

 of the divisions. In between the sand and the clay we have what are 

 generally known as loamy sand, sandy loam, loam, clayey loam, loamy 

 clay and clay. These divisions are based upon the size of the soil grains 

 and the different percentages of each size in a given soil. They are, of 

 course, not arbitrarily fixed, there being innumerable variations of soils. 



Now, if we consider soils as broken and decomposed rocks, the first 

 question that comes to our mind is, how and when were the rocks which 

 originally covered the face of the earth converted into soil? Certainly 

 ages and ages before man appeared on the earth. In fact before animal 

 life of any kind could exist there must have been vegetation; and vege- 

 tation of the higher forms could not exist on bare rocks. Probably the 

 commencement of the disintegration w'as coincident with the appearance 

 of plant life in the lowest form. 



Geologists tell us that the earth was once a molten mass, also that 

 the water which now composes the oceans was probably in the form of a 

 dense vapor which surrounded the red hot earth. Naturally, the earth 

 began to cool and as it cooled it contracted. The result of this was 

 that the surface subsided in some places and wrinkled in others, thus pro- 

 ducing the sea basins, valleys and hills. When the surface had cooled 

 sufl^ciently (and this cooling was hastened by the vapor in the air) the 

 vapor condensed and fell as rain or snow, and thus began to wear or 

 weather the rock. Frost and heat assisted the water in disintegrating 

 and breaking up the surface. Sometimes after the surface had cooled suf- 

 ficiently vegetation began its existence. First, in almost microscopic 

 forms, the mosses and lichens which are able to extract nourishment from 



