— u —

is the keynote of all scientific manuring, and while nitrogenous manures will

have a relatively important efEect on wheat and barley, maize makes greater

demand for phosphates, and leguminous crops and potatoes for potash.

Similarly, while wheat flourishes on a firm seed-bed and will rarely repay deep

cultivation, subsoiling is well-nigh essential for the greatest nett profit on sugar-

beet and potato cultivation. Again, the relative requirements of moisture and

the tolerance of drought exhibited by the different staples, to which may be

added the comparative tolerance of various plants for the salts common in

alkali soil, will markedly influence irrigation practice. A seasonable range in mean

temperature will also permit the adoption of planting seasons which will ensure

to each crop the most favourable conditions of growth within the limits obtaining.

Plant Tolerance and Variation.—^Plants or such artificial plant communities

as crops, however, adjust their forms and modes of behaviour to actually

operating factors, such as the amounts of available water, heat, light, nutriment,

and so forth. To an examination of the initial demands made on their environ-

ment, we have therefore to add an investigation of the means they employ to

utilise the surrounding conditions and to adapt their external and internal

structure and general form for that purpose.*

Existing staples, such as Egyptian and American cottons, are displaying

marked departures from the characters originally evidenced, and the possibility

of fixing new and desirable features by hybridisation on Mendelian lines opens

another valuable field of research. On the other h9.nd a demand has arisen for

cotton of the greatest possible uniformity, as a feature of the first importance to

spinners, and the control of variation by similar means in the seed-plots, coupled

with the systematic distribution of seed of uniform character, should go far to

ensure a favourable reception for our crop in the European markets.

A better understanding between planters and spinners has of recent years

facilitated the profitable introduction of cotton as a new product to our tropical

colonies and dependencies; The earlier sequence of events whereby the grower

has grown what chanced to grow, and the spinner has adapted his machinery to

deal with it, has largely passed. Efforts to irnprove the cottons grown are based

upon the known requirements of the spinner, and considerations of value are

constantly associated with those of productivity. " There is no necessary

confiict in cotton between quality and quantity. The Sakelarides cotton in

Egypt, and the Cambodia in India, have proved that it is possible to make cotton

more valuable to a spinner and at the same time more prolific and therefore

less expensive to the grower."f

* This study of acclimatisation gains an enhanced importance from the paucity of economic plants at present represented in the northern Sudan. The work of introduction and expei-imental trial of numerous types of potential value is occupying attention, and should later relieve the poverty and monotony of current, agricultural effort.

\ J. W. McConnel : " Commerce and Science and Cotton Growing."