516 Fischer The Biology of A r miliaria mucida , Schrader. 
of attacking a healthy branch when broken or wounded and causing death and 
decay.’ This statement is probably inspired by Massee's report quoted above. 
Sorauer, in 1906 (25), also evidently accorded it parasitic rank, since he 
refers to it in his work: 4 Von der Gattung Armillaria ware in erster Linie 
A. mucida zu erwahnen,’ but he adds: V. . iiber die Art des Parasitismus 
wissen wir nichts.’ Finally, we have the following authors who make no 
reference to it as a parasite : Tubeuf (26), Prillieux (21), and Frank (9) omit 
all mention of it; Saccardo (23) states: * Hab. ad truncos Fagi’; Gillot 
and Lucaud, 1891 (12) : ‘ . . . exclusivement sur les vieux troncs de hetres’ ; 
Gautier (11), in 1884 : ‘ . . . sur les troncs de hetres languissants ou coupes 
depuis peu Mcllvaine (16): ‘ ... on beech trees and roots . . . pushing up 
through the soil ’ ; Rabenhorst (22) : ‘ An Buchenstangen.’ 
It seems, therefore, highly desirable that further tests be applied to 
determine whether the fungus is a parasite or a saprophyte. The experi- 
ments described later clearly demonstrate that it can attack dead beech 
wood, but so far give no evidence of a true parasitic nature. However, let 
me at once admit that my experiments were neither sufficiently numerous 
nor extended over a sufficient space of time to traverse the theory of 
parasitism. Indeed, I am far from claiming to have proved that Armillaria 
mucida is not a parasite, but I am of opinion that more evidence, and of a 
positive character, is required before we accept that view. It is true that 
perfectly healthy trees in full vigour bear branches from which the 
fructifications of this fungus extrude, but in all cases the tissues in the 
neighbourhood of the tufts of carpophores are dead, and this is also the case 
when the tufts are seated on diseased parts of the main trunk itself. It 
should not be forgotten, moreover, that our knowledge of the causes 
predisposing to disease is almost negligible. Buller (4) failed to infect 
living maple and horse-chestnut trees with the spores of Polyporus 
squdmosus > and in his paper remarks : ‘ Possibly in nature other organisms 
serve to prepare the wounds for infection by the fungus.’ This ‘ preparation ’ 
might be the killing of the tissues in advance of the fungus under con- 
sideration, which then would be an obligate saprophyte and no longer even 
a facidtative parasite. This should be borne in mind in connexion with 
Massee’s account of his experiment commented on earlier. This point will 
be dealt with further when we come to discuss the results of the inoculation 
experiments. 
Description of the Fungus. 
A description of the fruit body of A. mticida will not be out of place, 
and the following is compiled from those of Cooke (5) and Massee (14) : — 
P ileus 1 to 4 inches across, flesh thin and almost diaphanous, 
hemispherical, then expanded, obtuse, often rugulose ; glutinous, whitish or 
tinged with grey (by some authors described as often much darker) ; often 
