. Contributions from the Botanical Laboratory and the Morris Arboretum of the University of Pennsylvania, vol. 14. Botany; Botany. w .. troo with doprossi,,,, a d> : /oVV if Vn^^^ "'', ^'Z^'-^- '"''"'"'' "" â¢'' -- .vc'nr old »J« -â ^ -^ â¢< r - 4 '⦠« - ⢠July, wlien 1 or 2, and in some eases as many as 4 lateral buds commence to o-row. The resultino- precocious shoots may attain a lenj^th of 3 to 4 inches, witli 1 or more winter buds at their apices, before becominj? dormant (Fig. 1, D). Needles develop on such shoots, but seldom attain more th
. Contributions from the Botanical Laboratory and the Morris Arboretum of the University of Pennsylvania, vol. 14. Botany; Botany. w .. troo with doprossi,,,, a d> : /oVV if Vn^^^ "'', ^'Z^'-^- '"''"'"'' "" â¢'' -- .vc'nr old »J« -â ^ -^ â¢< r - 4 '⦠« - ⢠July, wlien 1 or 2, and in some eases as many as 4 lateral buds commence to o-row. The resultino- precocious shoots may attain a lenj^th of 3 to 4 inches, witli 1 or more winter buds at their apices, before becominj? dormant (Fig. 1, D). Needles develop on such shoots, but seldom attain more than half of their normal leno-th and fail to elonofate further at the initiation of g-rowth the followinj*' sprint-. The precocions shoots may continue to elon- gate until quite late in the current season, although, according to Gustafson (5), elongation in pine shoots has been ccmipleted by early Jnly in Michigan. Measurements of 10 precocious shoots in a planting of 8-year-old red pine were taken on August 15, 1937, and again on October 25. All but one of them showed an increase in length from ] to VI in. The formation of a bud cluter at the tip of the precocious shoot (Fig. 1, D) interfei-ed with normal subsequent growth, as it caused secondary branches to be formed within a few inches of the bole (Fig. 1, E). The termiiud bud of the cluster in which the extra-seasonal growth oc- curs seldom takes part in the abnormal development, and usually elongates at the normal time the following season. The laterals, however, during the course of their extra-seasonal growth, react as if the terminal bud had been injured or removed and grow in a more or less vertical direction. Thus the shoot, originating from the terminal bud the following season, grows in competition with one or more laterals that had commenced growth the preceding summer. This results in a bi- or trifurcated appearance of the tree, which will be referred to as ^'forking" (Fig. 1, A). This condition
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