78 Journal of Agricultural Research voi. xii, No. 2 



sporophore to the complete expansion of the pileus, the sporophores 

 always pointed directly toward the light. In the case of the vertical 

 tubes it was to be expected that normally these sporophores would grow 

 vertically, since it was presumed that gravity as well as sunlight might 

 be a factor in the upward growth of the sporophore. When the tube 

 was placed horizontally, a totally dififerent condition existed. In this 

 case the sporophore developed directly toward the sunlight but at right 

 angles to the force of gravity. In the experiment with the flask the 

 upper two-thirds of the flask was covered with dark paper. Ten or 

 fifteen sporophores developed on the slanting surface of the agar in the 

 flask, all of them without exception pointing downward toward the source 

 of light. 



Lentinus lepideus was also grown on a more or less vertical slant with 

 the face of the slant turned towards the light. Perfect sporophores 

 which developed under these conditions always turned directly toward 

 the sunUght. 



INFIyUENCE OF GRAVITY ON THE FORMATION OF PORES 



In all of the experiments conducted with the Polyporaceae the formation 

 of the pores was always parallel to the action of gravity. If the tubes 

 were left in their original horizontal position with the slant side upward, 

 pores developed on the slant with their mouths pointing upward, thus mak- 

 ing them parallel to gravity. If, on the other hand, the culture tubes were 

 placed in a vertical position, the pores were formed on the sides of the 

 slant in such a manner that their mouths pointed more or less downward, 

 or both upward and downward in some cases and parallel to the force of 

 gravity. In fact, the position of the pores of a fungus which produces a 

 vigorous sporophore in artificial cultures could be governed at will by 

 simply changing the position of the tube in reference to gravity. It seems 

 therefore that while light is usually the main factor governing the initia- 

 tion of a hymenium, gravity is the dominant force which determines in 

 what direction the pores will point, irrespective of the incident light or 

 whether the spores when discharged will fall onto the walls of the porec 

 or not. 



INFLUENCE OF SUBSTRATUM ON PORE FORMATION 



Although it is a well-known fact that cultures of strictly parasitic 

 fungi can fruit on a wide range of media irrespective of the special host 

 on which the parasite usually thrives, the idea seems to have been gener- 

 ally accepted that some special culture media would have to be used in 

 order to obtain sporophores of the Polyporaceae on artificial media in test 

 tubes, flasks, etc. The experiments here given show that the same gen- 

 eral rule as to food material appUes to the wood-rotting fungi as a whole — 

 viz, that no special decoction is necessary for each species in order to 

 obtain sporophores; in fact, the wide range of artificial media upon which 

 many of the Polyporaceae have fruited is rather remarkable when the 

 nature of these fungi is taken into consideration. 



