— 134 — TJie crux of the experiiuent then Hes in the number of bolls developed per plant, or still further back, the number of flowers borne by each plant. If, within certain limits, the number is not influenced by spacing, obviously the yield per unit area will depend on the number of plants present. This has been found to be the case in practice. With spacing above 100 cm. by 45 cm. the yield per feddan is affected only by the number of plants, but with closer sowings root limitation plays an all important part, and the yield is depressed.

The Influence of Improved Cultivation,—No work has been more encouraging or given more confidence in the accuracy of laboratory and field observations than the results of the cultivation experiment. As with the manurial experiment, the check plots showed so little variation that all the records were grouped together and a representative mean obtained. Full details of the cultural treatment allotted to the various plots will be found elsewhere, but for the sake of clearness the main points are briefly summarised below.

The check plots, being Feddans 2, 4, 6, 8 and 10, represent normal cultivation in that they were ploughed, harrowed, ridged and planted similarly to the main crop.

Feddan I.—Flooded, ploughed, harrowed with disc and zigzag harrow, levelled, cross-ploughed with disc plough, subsoiled, harrowed, ridged and planted. Subsequent treatment included horse-hoeing and ridging as occasion required.

Feddan III.—Flooded, ploughed, harrowed, graded, disc ploughed, tooth harrowed, ridged and planted.

Feddan V.—As Feddan I, but not flooded before ploughing.

Feddan VII.—As Feddan I, but the ground was not levelled.

Feddan IX.—As Feddan I, but no subsequent cultivation was accorded to the growing plants.

It will readily be conceded that any improvement in the tilth will be most beneficial in the initial stages of the plants' development. All the evidence accumulated during the past three years goes to show that, generally speaking, the whole future of the crop, both as regards quality and quantity, is determined by the environmental influences operating long before the opening of the first bolls.

In the Sudan the life history of the cotton plant may be divided into two sections. First, a period of active growth during which the formation of branches bearing flowers proceeds smoothly, and a nightly increase in the