2 73 
On Polyporus squamosus Huds. 
of P. squamosus showed that up to a certain point development 
took place independent of light conditions (7, p. 57). The fructi¬ 
fications produced in the dark were always sterile, however, and 
highly abnormal in form, and Buller states that “ the formation of 
the pileus is brought about entirely by a morphogenic stimulus of 
light- 
in the cultures kept in darkness no fructifications were 
developed, with the possible exception of the two structures 
mentioned above. Hence it was the absence of light which 
probably caused the difference in the development of fructifications 
in the dull-light and dark series of cultures. 
With regard to the cultures grown in bright light, possibly the 
mycelial growth was not active enough to produce fructifications 
in the given time. A direct retarding action of bright light is not 
likely in view of the occurrence of fructifications in conditions of 
bright light in nature. 
(d). Culture on other media. The culture of the mycelium from 
the wood was tried in media consisting of a strong wood extract 
made into a stiff jelly with Gelatine or Agar. Cultures in Petri 
dishes and also on large surfaces of the medium in flasks were tried. 
In the case of the Gelatine media, comparatively rapid lique¬ 
faction took place (6, p. 117), and the mycelia grew only slowly. 
In Agar, the mycelia also grew very slowly, forming very thin 
cultures, and soon showing some slight oidial formation. 
No further results were obtained from either of these methods 
of culture. 
(i e ). The formation of Oidia. As already mentioned, the 
mycelia growing on wood, in nearly all cases produce bodies which 
seem from their method of formation to be “ oidia.” Cf. Brefeld 
(2, p. 203), Buller (6). 
Their method of formation was made out by teasing the 
mycelium from regions close to those which were turning brown, 
and also in hanging drop cultures. Text-figs. 1—3 illustrate the 
mode of formation of the oidia. 
The germination of the oidia, transferred from wood blocks to 
hanging drops of the following, failed in every case :—pure water, 
cane sugar, grape extract, Elm wood extract, water with sections 
of Elm wood. 
In somewhat similar cultures of Polystictus versicolor Miss 
Bayliss (1, p. 3) found that oidia, of much the same type as these, 
were produced very sparingly and only in rare cases. 
