io8 



RESEARCHES ON FUNGI 



Buder placed P. rtitens in two parallel-sided chambers with the 

 sporangiophores directed vertically upwards. In one chamber the 

 sporangiophores were, as usual, surrounded by air. The other chamber 



Fig. 53. — Phycomyces iiitens. Diagrams to illustrate two com- 

 parative experiments on heliotropi.sm. The arrow 

 indicates the direction of the incident rays of light. 

 In A the sporangiophores developed in the air and have 

 turned toward the source of light. In B the spor- 

 angiophores developed in paraffimmi Uquidum (paraffin 

 oil) and have turned away from the source of light. After 

 J. Buder (Ber. d. D. Bot. Ge.sell., Bd. XXXVI, 1918, 

 p. 104). Re-drawn by the author. 



was filled with paraffinum liquidum so that the sporangiophores 

 were immersed in it. Both chambers were then illuminated on 

 one side with equal intensity, with the result that the sporangio- 

 phores which were in the air turned toivard the light, while those 

 which were in the paraffin turned away from the light (Fig. 53). 

 The explanation of this difference in reaction is simple. In a 



