the plants that possess the largest and most vigorous roots endure best the drouth and burning heat.  The first function of the leaves is to gather materials for the building and strengthening of the roots, and only after this has been done do the stems lengthen and the leaves thicken.  Usually, the short season is largely gone before the stem and leaf growth begins, and, consequently, a somewhat dwarfed appearance is characteristic of dry-farm crops.  The size of sugar beets, potato tubers, and such underground parts depends upon the available water and food supply when the plant has established a satisfactory root and leaf system.  If the water and food are scarce, a thin beet results; if abundant, a well-filled beet may result.

Dry-farming is characterized by a somewhat short season.  Even if good growing weather prevails, the decrease of water in the soil has the effect of hastening maturity.  The formation of flowers and seed begins, therefore, earlier and is completed more quickly under arid than under humid conditions.  Moreover, and resulting probably from the greater abundance of materials stored in the root system, the proportion of heads to leaves and stems is highest in dry-farm crops.  In fact, it is a general law that the proportion of heads to straw in grain crops increases as the water supply decreases.  This is shown very well even under humid or irrigation conditions when different seasons or different applications of irrigation water are compared.  For instance, Hall quotes from the Rothamsted experiments to the effect that in 1879, which was a wet year (41 inches), the wheat crop yielded 38 pounds of grain for every 100 pounds of straw; whereas, in 1893, which was a dry year (23 inches), the wheat crop yielded 95 pounds of grain to every 100 pounds of straw.  The Utah station likewise has established the same law under arid conditions.  In one series of experiments it was shown as an average of three years’ trial that a field which had received 22.5 inches of irrigation water produced a wheat crop that gave 67 pounds of grain to every 100 pounds of straw; while another field which received only 7.5 inches of irrigation water produced a crop that gave 100 pounds of grain for every 100 pounds of straw.  Since wheat is grown essentially for the grain, such a variation is of tremendous importance.  The amount of available water affects every part of the plant.  Thus, as an illustration, Carleton states that the per cent of meat in oats grown in Wisconsin under humid conditions was 67.24, while in North Dakota, Kansas, and Montana, under arid and semiarid conditions, it was 71.51.  Similar variations of plant parts may be observed as a direct result of varying the amount of available water.  In general then, it may be said that the roots of dry-farm crops are well developed; the parts above ground somewhat dwarfed; the proportion of seed to straw high, and the proportion of meat or nutritive materials in the plant parts likewise high.