The evidence for senescence in plants has until recently been nil. Benedict (1915) has, however, brought forth a considerable amount of data indicating that the venation in leaves of woody plants is greatly influenced by the age of the plant. As the plant passes from youth to old age, the time being reckoned since its origin from seed, the areas of leaf tissue enclosed by the smallest branches of the fibrovascular bundles become relatively smaller. These he terms vein-islets. In other words, the proportion of fibrovascular tissue in the leaves increases with the age of the plant. Propagation by cuttings, furthermore, does not alter at all the venation in the leaf. It is only when reproduction is by seed that a juvenile venation is obtained.
Review of literature The literature dealing with potato experiments shows that rainfall (soil moisture) and temperature exert considerable influence upon growth and yield. The irrigation experiments of WIDTSOE (8, 9, 10) and HARRIS (4, 5) of Utah were especially significant since similar results were obtained from repetitions extending over two 5-year intervals. Their results showed that the middle period of growth, about the time of blossoming and tuber setting, was the most sensitive to moisture variations as reflected by the yield; if but one irrigation was given during the growing season, the best results were obtained when this was applied during the middle period of growth. SMITH (7) obtained similar results when he compared the rainfall with the potato yields in Ohio over a 50-year period. He too found a 30-40-day period about the time of blossoming to be the most sensitive to
ReENATIONAND SENESCENCE OF POLYEMBRYONIC CITRUS PLANTS M. R. ENSIGN The evidence for senescence in plants has until recently been zzl. Benedict (1915) has, however, brought forth a considerable amount of data indicating that the venation in leaves of woody plants is greatly influenced by the age of the plant. As the plant passes from youth to old Ensign, M. R. 1919. "Venation and senescence of polyembryonic citrus plants."
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