— Ill — means of an auxanometer, and the soil temperatures were recorded by a thermometer, the bulb of which was immersed in the soil.

While the plant is growing vigorously it is not unusual to observe the increase of 1 cm. in height in a single night, but as the season advances and the temperature after midnight decreases, the growth rate falls to 0-2 cm. or 0- 1 cm.

each night, and at a temperature of about 58 deg.F. growth is inappreciable.

Soil Conditions and Growth.—The cessation of growth is not, however, only caused by a lowered temperature. On stifE clay soils, in which penetration is difficult and the movement of water slow, incomplete development and stunting are often caused by root limitation. The water requirements of a cotton plant are very great, and should the root system prove inadequate, owing to the mechanical difficulties imposed by the texture of the soil, the effect is at once observable in the stunted, straggly condition of the aerial portion.

Fortunately no trouble has as yet been experienced from water-logging of the soil, which might result either from a rising water-table or from excessive irrigation. As it has been shown, the natural water-table lies very low, and, even with heavy irrigation, the water content of the subsoil never approaches saturation point under the conditions stated. Water, however, tends to accumulate at a depth of about two metres and without an efficient drainage system, continued irrigation would finally result in the formation of an artificial water-table, which would not only give rise to root asphyxiation, but would be the cause of an increasing accumulation of alkali in the surface layers as a result of capillary action and evaporation.

Humidity and Growth.—While temperature is undoubtedly the limiting factor during early growth, the water supply becomes of increasing importance as the season advances and the humidity of the atmosphere becomes less. At the onset of the dry winter winds a considerable amount of foliage is always shed to maintain the equilibrium between absorption and transpiration of water.

This loss of assimilatory surface must affect the productive power of the plant, and both the yield and the quality of the lint suffer in consequence.

By a fortunate chance the season 1914-15 was unusually humid, and a definite proof has been obtained of the above statements. Little change was noted in the height of the plants, but the vegetative development greatly exceeded that of previous years. It will be sufficient at the moment to present the flowering and the humidity curves of the last two seasons, leaving the evidence secured from the lint to be considered later.