WINNIPEG, 1909. 759 
not because it requires relatively little water, but because it flourishes best 
in a dry atmosphere, and possesses a large root system well able to supply the 
plant with water from that stored in the subsoil. It is generally recognised 
that wheat grows best in comparatively heavy soils, which retain a con- 
siderable store of the winter’s rains for the service of the crop in the 
summer. . 
The effect of high rainfall is harmful in several directions. If it comes 
in autumn it washes nitrates out of the ground and militates against the 
development of a full root system, the chief process going on in late autumn 
and early winter. There is, therefore, a reduction of crop; indeed, over a 
period of years almost a mathematical reduction. Shaw has shown that the 
average crop in England varies above and below a certain limit in inverse 
proportion to the rainfall of September, October, and November, his 
formula for the Eastern Counties of England being—yield =46 bushels— 
22 rainfail in inches. This formula only holds if the weather conditions 
later in the growth of the plant are normal; i.e., a high yield is only 
possible if the autumnal rainfall has been low, but a low autumnal rainfall 
may on occasion be followed by a low yield because some factor depressing 
the yield has intervened later. If much rain falls at or a little before 
harvest time the corn does not ripen well, and is in any case difficult to get 
in. It is this circumstance that limits the northward extension of wheat 
in the British Isles. The limit can be pushed somewhat further by the use 
of phosphatic manures, which tend to hasten maturity and thus enable the 
harvest to be got in a few days earlier. 
On the other hand, a good rainfall towards the end of spring is beneficial, 
especially if the spring is early; such a rainfall is a usual feature of the 
good wheat seasons. It is significant also that the exceptional years already 
referred to, in which the second increment of nitrogen produces less effect 
than the first, are generally years of low spring rainfall. 
(3) TemprraturE.—High temperatures are not at all necessary for the 
production of wheat, excepting at the time of maturation. In the best 
seasons it commonly happens that the summer (June and July) temperature 
is below rather than above the average. For winter-sown wheat, a mild 
open winter, not too wet, is desirable to bring the plant forward in early 
spring but is by no means essential. 
Spring Wheat.—The conditions regulating the growth of spring wheat 
are not quite the same; owing to the shortened period of growth the yields 
are rarely so high, and the crop appears to be more susceptible to rust and 
other diseases. For a good yield it is essential that the soil shall contain 
enough moisture to ensure a good start to the seed, but any excess of rain- 
fall in the first month or two of growth is prejudicial because it restricts 
the development of the root system. Little is known directly of the manurial 
requirements of spring wheat, but probably, like barley and oats, it is less 
dependent upon nitrogen but more on phosphoric acid than autumn wheat. 
The wheat plant in climates like that of England continues to take some 
food from the soil—nitrogen and phosphoric acid, for example—almost up 
to the time of harvest. Assimilation also continues as long as any part of 
the stem or leaves is green. 
The process of seed formation consists in transferring previously stored 
starch, protein, &c., from stem and leaf to the seed, but the material trans- 
ferred has much the same composition in the earlier and later stages of the 
process. That wheat which has been prematurely ripened through excessive 
drought or an attack of rust is exceptionally rich in nitrogen is probably due 
to the loss of carbohydrate from the grain by continued respiration, and not 
to gluten entering the grain first, to be followed by carbohydrates only in the 
later stages of filling. 
The ripening process appears to be mainly one of desiccation, 
