. Contributions from the Botanical Laboratory and the Morris Arboretum of the University of Pennsylvania, vol. 14. Botany; Botany. area of non-union of cambinm remains in the main axis of the tree as a fissure or pocket that becomes fille,l with a l,etorogeneons material composed oi resn, and fragments of the bark (Pigs. 1, F and 1, I) These fissures are m a more or less vertical plane for several years until one of the torke<I membei-s assumes dominance, as described above. While in this ver- tical position they are easily penetrated by water, and a favorable ment .s thus
. Contributions from the Botanical Laboratory and the Morris Arboretum of the University of Pennsylvania, vol. 14. Botany; Botany. area of non-union of cambinm remains in the main axis of the tree as a fissure or pocket that becomes fille,l with a l,etorogeneons material composed oi resn, and fragments of the bark (Pigs. 1, F and 1, I) These fissures are m a more or less vertical plane for several years until one of the torke<I membei-s assumes dominance, as described above. While in this ver- tical position they are easily penetrated by water, and a favorable ment .s thus established for the development of many species of parasitic and saprophytic bacteria and fungi. The presence of this flora may be an additional factor in causing the fissure to remain open Although it is not within the province of this investigation to evaluate the damage caused by forking from the point of view of the defects in the timber of forked trees, mention should be of the increase of winter damage in forked staiuls. Since part of a forked branch may not be united organically with the trunk, the mechanical resistance to stress caused by M^.ght of snow or ice is A branch that breaks in such a manner U'lg. 1, G) produces a more serious injury to the tree than does the break- ing "f a «,uud branch, as it lays open a cavity that may extend almost to the pi I, (I. ,g. 1, H). Normal branches are able to stand much greater stress and, it breaking occurs, usually snap off at a point beyond the trimk. FORKING IN RELATION TO ENVIRONMENT There appears to be no marked correlation between and site con- ditions, except a possible relationship with the mean seasonal temperature f 4- * t •' ? r^ • 4 i I z'^ of the locality. Determinations of soil pH in plots of forkin- red pine showed a range from to withont appreciable difference in the per- centage of forked trees. The disturbance occurred on soils varyin- from sandy types ni parts of
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