1902.] NATURAL SCIENCES OF PHILADELPHIA. 47o 



the new pheilogen. The resin thus forced out runs down the 

 trunk of 1 he tree, the more volatile substances evaporating, leaving the 

 solid resiu, which hardens and gives the trunk a glazed appearance 

 easily seen at some distance from the tree." Feziza (Dasyscypha) 

 Willkommil and jtJcldiiivi {Peridermium) elatinum cause similarly 

 an increased growth of the cortex. In summer the growth of the 

 mycelium of the former ceases and an unusually broad layer of 

 cork is formed, for the protection of the tree, along the boundary 

 between the sound and diseased tissues. Year by year the canker 

 spot enlarges and the conflict between parasite and host plant may 

 remain long undecided. Hartig found in the Tyrol lai'ches still 

 alive with blisters of a hundred years' standing. The second fun- 

 gus, whose mycelium stimulates giowth in a very marked manner, 

 is perennial in the cortical and bast tissues of the stem, and even 

 penetrates the cambium and the wood. The influence of the 

 fungus is to induce the increased formation of the wood, but espe- 

 cially the more vigorous development of the cortex. 



This account with reference to the inci'eased activity of the 

 pheilogen (cork cambium), due to the fungi mentioned, describes 

 in a fairly accurate manner the method of augmented growth in the 

 white cedar caused by Gymnospomngium biseptaium. Four suc- 

 cessive cork cambial layers have been developed in this sixteen- 

 year-old stem, with the possibility of more that have been exfoliated. 

 The newest pheilogen has developed inside the phlrem, cutting 

 off from the more internal layers three concentric layers of hard 

 bast. iSot only has the hard bast been cut off from the inside of 

 the stem, but also the resin canals, with, however, only a slight 

 exudation of resin, the corky flakes remaining almost quite dry. 

 The three outer cork cambia have only affected the primary cortex, 

 and between these layers of pheilogen the resin canals have ex- 

 panded to their widest diameter. The layers of cork cambium 

 take a somewhat sinuous course in running around the stem, so that 

 they apparently loop in and out among the rapidly dying cells. 



The hyphre of the fungus live appai-ently in the cells of Ihe 

 wood cambium and those of the phkem recently cut off from the 

 cambium. This is evidenced by a study of the cells. The hyphre 

 in cross-section occupy the lumen of the cells, for, in addition to the 

 cellulose cell wall of the host, there are rounded or elliplical rings 

 filled with granular matter (figs. 18, 19). These rings are the 



