24 RESEARCHES ON FUNGI 



Lepeschkin,! jjj endeavouring to elucidate the mechanism of 

 active water-excretion in plants, used Pilobolus as his chief material 

 for experimentation. Among his numerous observations on water 

 excretion by Pilobolus and the factors which influence it were the 

 following. 



The young naked stipe, that grows, upwards from the basal 

 swelling, usually excretes at its apex a large transparent drop. If 

 this drop is removed with a capillary pipette, it is replaced by a new 

 drop in the next 30-50 minutes. With further growth of the stipe, 

 smaller drops appear at intervals down the whole length of the stipe. 

 After separation of the sporangium by a wall, excretion of water 

 from the sporangium proceeds very slowly or ceases. Three to 

 five hours before the sporangium is shot away, the excretion of 

 water from the sporangiophore diminishes gradually and then 

 ceases.2 {Cf. Fig. 42, C, p. 86.) 



The excretion of water from the sporangiophore was studied 

 under the microscope. The fruit-bodies were enclosed in a damp- 

 chamber (with the coverglass smeared with glycerine). The drops 

 were measured with an ocular-micrometer and were drawn off with 

 a capillary pipette already introduced into the chamber. It was 

 found that water excretion always occurs at the same places on the 

 surface of the sporangiophore and quite regularly and continuously. 

 The drops became about 0-2 mm. in diameter and were drawn off 

 five to ten times in succession. The time taken for the renewal of 

 a drop at a particular place on the sporangiophore was very constant 

 and varied with the place from seven to twelve minutes. At 

 different places on the sporangiophore the amount of water excreted 

 is very unequal. The most energetic excretion of water takes place 

 directly under and above the orange-yellow zone which lies at the 

 top of the stipe and just beneath the subsporangial swelling.^ 



The chemical composition of the cell-sap in the great vacuole 

 of the sporangiophore of Pilobolus longipes and that of the excreted 

 drops were determined and compared. The turbid liquid expressed 

 from a number of sporangiophores was dried at 60° C. and the 



^ W. W. Lepesclikin, " Zur Kenntnis des Mechanismus der aktiven Wasseraus- 

 scheidung der Pflanzen," Beihefte z. Bot. Centralb., Bd. XIX, 1906, pp. 409-452. 

 2 Ibid., pp. 412, 418-419. ^ /^y^^ pp 412-413. 



