116 MISSOURI BOTANICAL GARDEN. 
growth of alternating denser spore formation of a texture 
similar to that of the former set of cultures; but between 
the denser concentric rings were regions where spores were 
only sparsely formed. 
Cultures under green light exhibited rings of growth of 
less distinctness, indicating that it is the blue rays of light 
that affect spore formation. Careful observation estab- 
lished that the rings of sparse spore formation are formed 
in the daytime, and the denser at night, proving that the 
blue rays of light inhibit spore formation in these fungi. 
Cultures of Cephalothecium.taken from decaying sugar 
bect roots and from rotting apples were much more sensi- 
tive to blue light than the same fungus taken from the 
fruits of Rosa rugosa. The species from all these sources 
was one and the same, if mycological characters were to 
decide the question; yet, the difference in growth on vari- 
ous media under blue light suggests that we have two dis- 
tinct physiological forms of Cephalothecium roseum. The 
form occurring on apples and sugar beets grows more 
often in the dark in nature, in stored apples and beets; the 
one on the fruits of the rose is found growing on the rose 
fruits in open light. May it not be that the latter has 
become more accustomed to strong light, and is less af- 
fected by the blue rays? 
There is another type of zonation in artificial cultures of 
some fungi which is not due to light stimuli, but probably 
to variations in the amount of food taken in by the my- 
celium, and to possible resting periods in spore formation. 
This type has been observed by the writer in a number of 
species of fungi; among these is Hypocrea. Thomas 
Milburn mentions this type of ring formation in his studies 
of Hypocrea rufa and other fungi.* In Hypocrea the 
concentric rings are formed, not daily, but in a much 
' longer period of time. 
* See Centralbl. fiir Bakt. Par. u. Infek, 18: 129-138. 
