Sixth, any mechanical vibration of the plant seems to have some effect upon the transpiration. At times it is increased and at times it is decreased by such mechanical disturbance. Seventh, transpiration varies also with the age of the plant. In the young plant it is comparatively small. Just before blooming it is very much larger and in time of bloom it is the largest in the history of the plant. As the plant grows older transpiration diminishes, and finally at the ripening stage it almost ceases. Eighth, transpiration varies greatly with the crop. Not all plants take water from the soil at the same rate. Very little is as yet known about the relative water requirements of crops on the basis of transpiration. As an illustration, MacDougall has reported that sagebrush uses about one fourth as much water as a tomato plant. Even greater differences exist between other plants. This is one of the interesting subjects yet to be investigated by those who are engaged in the reclamation of dry-farm districts. Moreover, the same crop grown under different conditions varies in its rate of transpiration. For instance, plants grown for some time under arid conditions greatly modify their rate of transpiration, as shown by Spalding, who reports that a plant reared under humid conditions gave off 3.7 times as much water as the same plant reared under arid conditions. This very interesting observation tends to confirm the view commonly held that plants grown under arid conditions will gradually adapt themselves to the prevailing conditions, and in spite of the greater water dissipating conditions will live with the expenditure of less water than would be the case under humid conditions. Further, Sorauer found, many years ago, that different varieties of the same crop possess very different rates of transpiration. This also is an interesting subject that should be more fully investigated in the future. Ninth, the vigor of growth of a crop appears to have a strong influence on transpiration. It does not follow, however, that the more vigorously a crop grows, the more rapidly does it transpire water, for it is well known that the most luxuriant plant growth occurs in the tropics, where the transpiration is exceedingly low. It seems to be true that under the same conditions, plants that grow most vigorously tend to use proportionately the smallest amount of water. Tenth, the root system--its depth and manner of growth--influences the rate of transpiration. The more vigorous and extensive the root system, the more rapidly can water be secured from the soil by the plant.