20 
Dorothea C. E. Marryat. 
although Marshall Ward, 1 working with Stereum, considered that in 
the infected wood the inner layers of the lignified cell-walls were 
by the action of the hyphae converted into cellulose, Potter 2 later 
declared that in perfectly sound wood the cells were never all 
completely lignified, but that when tested some invariably gave the 
typical cellulose reaction previously attributed to the action of the 
fungus. 
Text-Fig. 1. Tangential section of Elm-block sixty-five days after 
infection, stained with Delafield’s Hajmatoxylin, and showing hyphae (of two 
sizes) in the vessels and wood-fibres. The smaller hyphae are producing 
numerous chlamydospores, in the larger ones several fine clamp-connections 
are to be seen. 
N.B.—The medullary rays are entirely uninvaded by the hyphae. 
Considering the very slight, or possibly very slow, destructive 
action of the hyphae of Pleurotus upon wood, it does not appear 
to be a very suitable species from which to try to collect evidence 
on this point, though better results may, perhaps, be obtained when 
the blocks have been infected for a greater length of time. 
It seemed, however, worth while to give a short account of the 
chlamydospore-formation, since it has apparently been only some¬ 
what rarely observed, and I can find no record of these spores 
having been obtained direct from pure cultures of the basidiospores. 
1 Loc. cit. 
2 Annals of Botany, 1904, Vol. XVIII., p. 121, 
