490 PROCEEDINGS OF THE ACADEMY OP [May, 



l)ocau.<o the stem was dead along the vadiiis of stem chosen for the 

 computation of the tracheids. 



The mycelium in the cortex is well marked. The hyphse grow 

 both into and tlu-ough the cortical cells, and are found in the larger 

 and smaller intercellular spaces. Their direction of growth is less 

 definite than in the wood, and they, therefore, form a complex of 

 twisted and curved hyphse which nin apparently through the medio- 

 cortex in an indefinite manner. The rounded enlargements of the 

 h}'phal cells above mentioned are also found. 



Pathological Conditions of Stem Induced by the Myce- 

 lium OF G. Ellisii. 



The pathological condition of the stem of white cedar induced 

 by the parasite are very different from those produced by the 

 mycelium of G. biseptatum. It may be stated at the outset that 

 the diseased conditions are much more severe when the mycelium 

 of G. Ellisii is the pathological agent, although the swellings 

 never become so large and globose as those formed by the stimu- 

 lating influence of the mycelium of G. biseptatum. The Avitches' 

 broom-like character of the malformations caused by G. Ellisii 

 have already been described (figs. 6, 8). Observations in the field, 

 after part of this paper had been written, reveal some characteristic 

 features of the disease not mentioned then. The disease, except in 

 young trees, seems if it attacks older trees, to be confined to the short 

 lateral bi-anches of the trees, as they form a pure growth in the 

 cedar swamps of New Jersey. Sometimes all of the larger branches 

 from the lower part of a tree to the top will be fasciated. The 

 branches live for a long time before death finally ensues, and they 

 consequently have a gnarled and knotted appearance which gives to 

 a large tree badly diseastid an unsightlj' appearance. Bii'ds, such 

 as the fish crow, take advantage of the flattened, closely crowded 

 condition of the branchlets to build their nests under cover of the 

 dense and crowded mass of leaves which forms a closely set crown of 

 foliage (fig. 6). Tlie photographs of diseased lateral branches 

 (figs. 6, 8), one of which supports a nest of the fish crow, show the 

 general appeai^ance of the disease when it has pi-ogressed to the 

 point of involving the whole branch. 



In the seven-year-old stem above described the wood is badly 

 broken down, and in place of the healthy tracheids there are irregu- 



