Of ten analyses made with the cotton lint (which takes up about 10-1/2 per cent. of the whole) M'Bryde states that the average amount of water found was 6.77, ash 1.8, nitrogen .2, phosphoric acid .05, potash .85, lime .15, and magnesia .16. He very pertinently remarks also "that if the lint were the only part of the plant removed from the land on which it is grown, cotton would be one of the least exhaustive of farm crops. The only other part which need be permanently lost to the soil is the oil, which also contains very small amounts of fertilising constituents." In connection with this he further says "that even when the seed is taken away along with the lint, cotton still removes smaller amounts of fertilising materials from the soil than either oats or corn." It should be borne in mind that the soil upon which cotton is cultivated lies fallow for a greater part of the year, and the fact of absence of cultivation, with consequent non-fertilising and non-enriching of land, must tend in the direction of soil exhaustion by the Cotton plant. Another useful and important fact in connection with the Cotton plant is the medicinal use to which the roots are put. According to the _American Journal of Pharmacy_, the bark from the roots of the Cotton plant contain an active ingredient which in its effects is very much like ergot. Chemical investigations have conclusively proved that the ripe fibre of the Cotton plant is composed of the following substances:-- Carbon, Hydrogen, Oxygen, and they tell us that when cotton is fully ripe it is almost pure cellulose. Dr. Bowman has pointed out that the percentage of water in cotton fibre "varies with different seasons from 1 to 4 per cent. in the new crop, and rather less as the season advances. Above 2 per cent. of moisture, however, seems to be an excessive quantity even in a new crop cotton, and when more than this is present it is either the result of a wet season and the cotton has been packed before drying, or else it has been artificially added." About one fifth of the whole plant by weight consists of the seed, and an analysis of this shows them to be composed of water, ash, nitrogen, phosphoric acid, potash, soda, lime, magnesia, sulphuric acid, ferric oxide, chlorine, and insoluble matter. As a commercial product seeds are exceedingly valuable, and yield the following substances:--oil, meal, hulls, and linters. When the hulls are ground they receive the name of cotton seed bran. The inside of the seed, when the hull has been removed, is often called the kernel and is sometimes also designated peeled seed, hulled seed, and meats. It is this kernel seed which, when properly treated, yields large supplies of oil and meal. CHAPTER II. COTTON-PLANT DISEASES AND PESTS. There are several classes of agents all of which act injuriously more or less on the Cotton plant. 1. Climatic changes, including hygrometric variations of the atmosphere, and extremes of heat and cold.