4 Of Soils, etc. Humus. Mm-k. 



of trees, we shall generally give with them their scientific or botani- 

 cal names, as a means for more exact designation. 



13. The common names are very uncertain, and may in one re- 

 gion be applied to species very unlike those where they arc used in 

 another. But the scientific names, rightly applied, are exactly un- 

 derstood in every language in which the sciences are taught, ;ind 

 can not be mistaken for any others. They are very generally de- 

 rived from Greek or Latin words, expressing some quality or char- 

 acter in the genus or species to which they are applied. The generic 

 name is more commonly derived from the Greek, and the specific 

 name from the Latin. The former always begins with a capital let- 

 ter the latter only when it is derived from a proper noun. Where 

 a number of species are mentioned in succession, the initial letter 

 only of the genus .will be used after the first one, as Pinus strobus, 

 P. mitis, P. rifjida, etc. 



CHAPTER II. 



OF SOILS AND THEIR PREPARATION EFFECTS OF SLOPE AND ASPECT. 



14. The soil or loose material that generally covers the surface of 

 the earth to a 'greater or less depth, partakes in a large degree of 

 the chemical character of the rock formations from which it has 

 been derived. These may be the subjacent rocks, or the material 

 may have been transported by former geological agencies, as in 

 "drift," or deposited by those now in action, as in alluvial mud, 

 or littoral sands. 



15. Besides these mineral .components, the soil generally contains 

 more or less organic material, derived from vegetation, or, to slight 

 extent, from animal life. In the native forests, this ' ' vegetable soil " 

 has been mostly created by the trees and herbage, from materials 

 taken up in solution by the roots from the soil, and absorbed by the 

 leaves from the air, and has gradually accumulated from the decay 

 of the leaves, or of the trees and plants themselves. 



16. This organic material is called humus, and its quality and 

 amount depends upon the kind and quantity that has been allowed 

 to decompose. It is sometimes known as " vegetable mold," and 

 has no definite chemical composition, but contains Humic acid 

 (C., H 12 O 6 ), and various other organic compounds. When voge- 

 tatiou decays in moist places, as in swamps, it forms muck, and 



