1902.] NATURAL SCIENCES OF PHILADELPHIA. 479 



Eleventh Year Wood. Late suininer. Plentiful iu a detiuite 

 zone. A fe\r in the autumn wood. 



Twelfth Year Wood. Spring. In a definite zonal band, two or 

 three tracheids deep. A few in the summer wood. A ring of scat- 

 tered tracheids at the beginning of the autumn wood. 



Thirteenth Year Wood. "Whole year. Here the small excres- 

 cence began its growth. It is limited on both sides by dead tissue. 

 The plugged tracheids form several circular zones both in the spring 

 and summer woods. Thiee well-marked circular zones of plugged 

 tracheids are clearly distinguishable, forming with their aggregation 

 an almost continuous area involving most of the tracheids of the 

 spring and early summer woods. Beyond the area with the largest 

 number of these plugged tracheids occurs the small excrescence 

 which has grown over the adjacent bark at the dead areas, pro- 

 ducing a characteristic fissure. The disposition of these plugged 

 elements in concentric rings in the several annual cylinders of wood 

 is somewhat analogous to the disposition of the resin canals in Abies 

 balsamea, diseased by Dasijscypha resinaria, as described by Ander- 

 son. This botanist finds that these are arranged in circular rows 

 and in all cases follow the development of the above-mentioned 

 fungus. According to the same author, Nottberg produced these 

 resin canals experimentally in the wood and branches of Abies 

 pectinata by fracturing the branches. The characteristic canal 

 chains were formed in the wood near the fracture three mouths 

 after the wound had been made.^^ 



The phlcem and cortex regions of the swollen areas are remark- 

 able for the increase in the number of elements. The cork, hard 

 and soft bast, representing the previous activity of the cambiar 

 layers, are pushed off more rapidly than in a normal undiseased 

 area (figs. 13, 14). New layers of hard and soft bast are formed 

 constantly by the wood cambium, and the noteworthy features of 

 such phloem is that the bast fibres do not form so continuous a circle 

 of growth, but are isolated in patches. The cells of the soft bast 

 are more irregular iu outline (fig. 13). The resin canals in such 

 cross-sections are also more inconstant in outline. Some of them 

 are large and of irregular shape ; others ai'e circular and small. 

 The resin canals in the normal slate are, as a rule (not always), 

 elliptical in cross- section. Where the cortex of the excrescence 



'-' Anderson, loc. cit., p. 31. 



