BIOLOGY OF COLLYBIA VELUTIPES. 161 
Unlike most of the large wood-destroying fungi, then, 
Collybia velutipes chiefly attacks the cellulose portions of the 
wood-elements, leaving a lignin skeleton. Thus the infected 
wood does not appear to have undergone any profound changes 
until examined microscopically, the presence of the middle 
lamella not allowing the remains of the elements to become 
detached and so cause the wood to crumble away. In nature, 
however, the chauges in the wood are far more complicated, 
owing to the action of the bacteria invariably met with in 
infected wood. It is quite within the bounds of possibility that 
the products they give rise to are utilized by the fungus itself, 
and so a kind of symbiosis (metabiosis) established. 
My work throughout has been made considerably easier by 
the many suggestions of Prof. Marshall Ward, who originally 
proposed it, and I take this opportunity of expressing my thanks 
to him. 
Botanieal Laboratory, Cambridge, 
Aug. 1898. 
EXPLANATION OF THE PLATES. 
Puate 2. 
Fig. 1. (a) Formation of oidia on the eighth day after infection in a hanging- 
drop culture, 
(b) Oidia-chains a day older. 
. Mature sporophore of Collybia velutipes, grown on a sterilized block 
of ZEsculus-wood. The age of the culture is 35 days. Photographed, 
natural size, from the original. * 
3. A series of diagrammatic sketches of sporophores produced from the 
primary sporophore, which in these cases has functioned as a 
sclerotium. 
4. A longitudinal section of the stipes of a mature sporophore showing 
the “ conducting system.” The hyphe composing it are beginning to 
form branches. 
. Terminations of the “ conducting system " in the subhymenium, between 
the barren cells of the hymenium, and in cystidia, 
6. A longitudinal section from the upper portion of a pileus, to show the 
layer of small external hyphz, large spindle-shaped hairs with 
yellowish-brown contents (a), the smaller hairs arising as branche 
from the apex of a hypha (b) and the fine much-branched, water- 
holding hairs (c). 
bo 
or 
* Kindly photographed by Mr. W. G. P. Ellis. 
