382 The Botanical Gazette. [November, 
surface in large numbers at certain times of the day, notably in the 
evening or towards the middle of the afternoon. I have not been able 
to discover any secretion that might be attractive to the insects given 
off by the plant, but there may be such. 
In walking over the minutely perforated surface an occasional fly 
may be seen to get its feet caught between the clefts and is then unable 
to extricate itself. It shortly dies and lies flat upon the hymenophore 
surface, Whether the death is due to poisoning or simply to fatigue, 
Ihave not determined. At any rate there is very promptly sent up 
around the body of the insect a mycelial growth from the interior of 
the pores of the plant, and in a few hours the insect is completely cov- 
ered by the fungus filaments. For atime it may be seen as a hum- 
mock or elevation on the hymenophore, but shortly, through the 
absorption of its substance into the tissue of the fungus, it disappears 
as an elevated area and is discernable solely through its imparting a 
slightly lighter color to the portion of the hymenium lying around it. 
T have in my collection one of these Polyporus fruits, about six inches 
in diameter, with seventeen small flies captured and digested —some 
of them so completely destroyed that there is scarcely more than a 
vague stain left to mark the spot where they lay, and others of a whit- 
ish hue and lying in high relief on the tinted lower surface. In the 
case of those that are thoroughly digested the plant produces pores 
afresh through the remains of their bodies, and the trace of their 
original presence becomes almost obliterated. Those that are partially 
digested are not penetrated by the pores but the mycelial covering 1s 
of a solid texture. It is quite like that of the border of the hymeno- 
phore. Nor dothe penetrating pores appear until the flies are reduced 
almost to the level of the general hymenium surface. 
This phenomenon is an interesting one, for it shows how a structure 
devised for another end may be devoted to an accessory line of wor 
and may in time come to acquire an accessory function. The Polypo- 
Tus can not be conceived to derive very marked benefit from the small 
substance that it is able to obtain from the unfortunate flies, but it 1s 
easy to see how such a practice if persisted in might develop into @ 
highly important nutritive habit. It is unquestionably true that the 
plant derives some nutriment from these flies, for where they fall and 
taise the level of the hymenium there are more pores produced than 
at other points of similar size, This would indicate that the habit of 
fly-catching which is practiced by the Polyporus applanatus might de- 
velop into something of real importance to the species. cS 
I shall be glad to hear from others who have noticed this habit 9 
Polyporinez.— Conway MACMILLAN, University of Minnesota. 
