484 PROCEEDINGS OF THE ACADEMY OF [May, 



section uppaveutly occupy the lumeu of the cells, for, iu addifiou to 

 the cellulose cell wall of the host, there are rounded or elliptical 

 rings filled with granular matter. The difficulty of clearly tracing 

 the hyphie in a cro5S-section is almost entirely removed by careful 

 study of longitudinal sections. Such longitudinal sections reveal 

 the following distribution of the hyphae and their relation to the 

 cells of the host : 



The hyphae are of a brown color, and can easily be traced by 

 means of the contrast which this color affords to the colorless 

 Iracheids and to tlie medullary ray cells which have stained a 

 bright-green color with methyl-green. The mycelium is not abun- 

 dant, and if we imagine the host cells to be macerated away, leav- 

 ing the mycelium, it would form a I'eticulum of large open meshes 

 much in appearance like a coai'se fish-net, only not so regular (fig 

 22). The hyphse are variously curved, gnarled or knuckled (fig. 

 22). Their course is somewhat sinuous, or an undulate one, 

 although in many cases the lai'ger hyphal strands are perfectly 

 straight. They occur in all parts of the wood of the swelling, and 

 are associated in general with the plugged tracheids and the en- 

 larged medullary rays, Avhich contain the yellowish granular matter 

 to which reference has already been made. The plugging of some 

 of the tracheids in the several annual rings of wood with yellowish 

 granular material and the enlargement and filling up of the medul- 

 lary ray cells seems to be correlated with the presence of the my- 

 celium. The tracheids and medullary ray cells distant from the 

 strands of the mycelium are -without these evidences of nutritive 

 changes, followed by the filling of the cell cavity by the granular 

 waste, or reserve (?) products. The hyphse are marked by numer- 

 ous transverse partition walls, and these are sufficient to indicate 

 that the fungus belongs to the higher series of fungal types. Some 

 of these hyphal cells are long and. cylindrical. Others are shorter 

 and more cheese -box-like in form. 



Relation' of Hyph.e to Host Cells. 



The hyi)hse grow into and through the medullary ray cells, and 

 it is through these cells that the mycelium maintains its continuity 

 from annual wood ring to annual wood ring. It is this growth 

 through the medullary rays that accounts for the perennial habit of 

 the fungus. At best the growth of the fungus is a slow one, as the 



