272 
S. Reginald Price. 
(, c ). Effect of light and darkness on the pure cultures. As the 
presence or absence of light, and the intensity of light has a direct 
effect on the growth and development of fungi in many cases, 
experiments were made to determine whether this mycelium showed 
such a response. 
Three sets of conditions were used for this purpose : (i) bright 
light, in a large window with a north aspect; (ii) subdued light, in 
the same room at a distance of some feet from the window ; (iii) 
darkness—almost continuous in a dark room, but unfortunately 
some dull light entered at times through the door being left open. 
In one set of experiments cultures were set up on Lime wood 
and Sycamore wood on May 3. On August 6 the series in light 
showed a very feeble growth in every case, while, that in darkness 
showed a much stronger development. 
Another series was set up on Elm wood, and cultures were 
kept under conditions i, ii and iii. The growth of the mycelium 
was strongest (externally at any rate) in the dark. The cultures in 
dull light showed a condition intermediate between these and the 
thin growths again obtained in bright light—often in the last case 
no more than a thin brown layer barely covering the surface. 
Abnormal fructifications, as described above, were produced in 
nearly every case, on blocks kept in dull light. In no case were 
fructifications of any kind produced in bright light, 1 and in darkness 
only two structures appeared which may have been incipient 
fructifications. 
Marshall Ward (14) in his work on Stereum hirsutum found 
that “ light is not necessary to the development of the fungus or 
the hymenia ” and apparently there were no noticeable differences 
between cultures kept under conditions of darkness or diffused 
light. 
It is interesting to find in the present case that although light 
is not necessary for the growth of the mycelium, yet it has a strong 
influence on the actual development of the abnormal fructifications. 
The more abundant growth of the mycelium in darkness seems 
to be due in part at any rate, to the retarding action of light on 
growth, a phenomenon of general occurrence (9, p. 98), so that the 
mycelium is feeblest when grown in bright light. 
It seems that light is necessary for the formation of the fructi¬ 
fications, perhaps supplying a stimulus for their development. 
Buller, using naturally infected logs half destroyed by the mycelium 
1 See, however, the note at the end of this paper (p. 281). 
