The question of boron mobility and re-use in planits has not been adequately investigated. It is often dismissed with the statenment that a continuous supply of boron is necessary during growth because boron cannot be stored and re-use(l. However, there is evidence that boron is not entirely immobile, although re-use has not been (lefinitely establishe(l. Eaton, McCallum, and Mlayhugh (3) showed that, under conditions of excess boron, stone fruit trees translocate boron to the fruit an(d that higlh concentrations can accumulate there -while only moderate concentrations remain in the leaves. Scott and Schrader (8) showed that the concentration of boron in older leaves of the grape plant (lecrease(l after the source in the root media hadl been removed. They On the (late designatedl for Period 1 the nutrient solution was (lumped an(l the gravel wvas flushed four timles with (listillech water and nutrient without boron then provided. At the end of each of 12 assigned intervals, the plants of a particular group were cut at the cotyledonary no(le and the fresh weight was taken. The leaves w\ere then strippedl from the stem and numbered consecuttively from the base of the plant. Leaves

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