276 ItKPORT OF THE BoTANICAL DEPARTMENT OF THE 



some live spots were encountered on reaching the phloem and after 

 cutting away the bark about 1 mm. deeper, irregular areas of live 

 and dead tissues were found intermingled on the cut surface, giving 

 it a marbled appearance. The injured spots were variously dis- 

 colored from pink to blue, brown and black. A dark colored " sap " 

 had been exuding from some very short and narrow clefts in the outer 

 bark of this area. Some of the clefts reached even deeper than the 

 bark had been cut away, for several of them may be seen as small 

 ragged rifts in the cut surface. 



The location of these injured patches, on the southwest side of 

 trunks, varied considerably. They were situated anywhere from a 

 few centimeters above the ground up to the first crotches. But the 

 location of the maximum injury corresponded to the height to which 

 normal bark roughening or scaling had attained on the trunk. It 

 may also be seen in the above figure that the bark surface below and 

 including the area of greatest injury is roughened or has begun to 

 scale off as the bark of trees does when a certain stage in its life history 

 is reached. Above the injured area are a few superficial checks here 

 and there, as is commonly the case in the region of transition from 

 rough to smooth bark. In the instance shown in figure A of Plate 

 XVII maximal injury resulted below the main crotches, about 85 cm. 

 above ground. Here the greatest injury also occurred in the region 

 of transition from rough to smooth bark, with a few lesser spots of 

 exposed wood in evidence lower down. This is one of the trees 

 found exuding discolored "sap" from injured bark covering these ex- 

 posed areas in 1909. At the right and left of the stem may be seen 

 some successful bridge grafts extending from near the ground to the 

 branches. The tree bore a normal crop in 1911 and will probably 

 live many years, although its lease on life has doubtless been fore- 

 shortened by leaving the exposed wood unpainted, for after the cen- 

 tral cylinder of wood has rotted a strong summer wind will probably 

 break it off. 



It seems unlikely that the veneer around the bases of these trees 

 had any causal relation to the bark injury, as was suggested by 

 Stewart.* First, becase affected areas were mainly on one side of 

 the trunks and were frequently above the veneer. Second, because 

 similar new cases of injury were found in 1911 as had been observed 

 in 1910, and affected areas seemed always to be on a region of bark 

 that was in a certain stage of its development whether that be under 

 or above the veneer. 



It seem-S that the two periods of exudation of " sap " from such 

 injured patches of bark occur during the two periods of high sap 

 pressure, in spring and in July. Doubtless the dying, in early sum- 

 mer, of groups of live cells which are scattered among winter-injured 



1 F. C. Stewart Notes on New York plant diseases, I. 

 N. Y. Agrl. Expt. Sta. Bui. 328:323-24. 1910. 



