30 RESEARCHES ON FUNGI 



mechanisms for excretion but felt that without more knowledge of 

 cell-dynamics it was impossible to treat the problem of exudation 

 satisfactorily. 



Weis 1 set a Pilobolus fruit-body on a slide, placed a glass thread 

 and some vaseline across the sporangiophore just under the sub- 

 sporangial swelling, pressed the glass thread down with a cover- 

 glass, and thus compressed the sporangiophore into two parts. 

 This enabled him to apply plasmolytic solutions to the subsporangial 

 swelling by itself and to the stipe by itself. He found that, with 

 a 0-4-0-5 gram-molecule cane-sugar solution, plasmolysis took place 

 in the swelling slowly or not at all and in the stipe considerably 

 faster. From this he concluded that the osmotic value of the 

 cell-sap (or the resistance to filtration of the wall as a whole) must 

 be greater in the swelling than in the stipe, but added that his 

 conclusion still leaves us free to regard the tiny places in the wall 

 where drops are excreted as more permeable than the rest of 

 the wall. 2 



Ursprung and Blum ^ submerged a Pilobolus fruit-body in 

 paraffin oil {liquidum paraffinum) and with a compression apparatus 

 applied pressure to the liquid. As the pressure was slowly increased, 

 drops came out of the wall of the subsporangial swelhng and the 

 adjacent part of the stipe at about the same time. If the screw of 

 the pressure apparatus was not further tightened, the sporangiophore 

 sucked in the drops again. With renewed increase of the pressure, 

 the drops appeared again, but none were observed on the basal 

 part of the stipe. From this experiment the authors concluded that, 

 if the turgor pressure is the same throughout the whole of the 

 sporangiophore, the suction pressure of the contents in the upper 

 part is smaller than in the lower part, and they add that this 

 difference may be due to differences in the osmotic values of the 



1 A. Weis, "ZurMechanikderWasserausscheidung aus lebenden Pflanzenzellen," 

 Planta, Bd. II, 1926, p. 247. 



2 Weis, unfortunately, does not state whether or not the compression of the 

 sporangiophore into two parts injures the cell in any way nor whether or not his 

 sporangiophores had ceased to excrete water before they were used for his 



experiment. 



3 A. Ursprung and G. Blum, " Eine Methode zur Messung Polarer Saugkraft- 

 differenzen," Jahrb.f. wiss. BoL, Bd. XLV, 1925, p. 11. 



