252 BOTANICAL GAZETTE [APRIL 
phore, not only in the Polyporaceae but also in the Hydnaceae and 
Agaricaceae, are positively geotropic. Since in non-stalked forms 
adjustment of the whole pileus is obviously impossible, the down- 
ward growth of the hymenophore alone is responsible for the orienta- 
tion of the hymenium. If the position of the growing pileus is 
changed, readjustment to the new condition is accomplished solely 
by the change in direction of growth of the elements of the trama- 
plates and the growing, undifferentiated elements of the pileus. This 
often results in the formation of new pilei growing at various angles 
from the old pileus (see ATKINSON, /. c.). 
In such types as the Polyporaceae it is evident that the form of 
the fungus depends to a large extent on the growth of the trama- 
plates making up the hymenophore. Since the mode of growth of 
these elements is greatly influenced by gravity, the question naturally 
arises as to what extent the form which these fungi assume is deter- 
mined by the responses of the elements to the influence of gravity. 
To determine the effect of gravity as a form-stimulus, klinostat 
experiments were conducted with a number of fungi from different 
families. As a rule sticks and branches upon which sporophores 
were growing were brought into the laboratory for experimentation. 
Although a considerable number of plants were thus tried, only a 
few gave results, owing, no doubt, to the fact that the conditions of 
growth of these forms are not sufficiently well understood so that | 
they can be cultivated with certainty. From a few forms interesting 
results were nevertheless obtained. The experiments are here first 
described, and this is followed by a discussion of the significance of 
the results obtained. 
In October 1905 a small fruit-body of Polystictus cinnabarinus 
growing on a stick was placed in a moist chamber and rotated 
on the horizontal axis of the klinostat until the middle of December. 
The fruit-body was a little over 1°™ in diameter, with few pores, and 
growing at the margin. During the experiment its growth was slow, 
although the plant appeared to remain healthy. At the end of the 
experiment the plant was about 2°™ in diameter. The new growth, 
however, was not confined to the margin as in stationary fruit- 
bodies, but owing, no doubt, to the still embryonic condition of 
the fruit-body growth was resumed over the entire surface, resulting 
