122 



RESEARCHES ON FUNGI 



Deformation of Vacuoles by Flowing Protoplasm.— In a highly 

 vacuolated hypha of Pyronema confluens, if the protoplasm is at rest 

 or moving very slowly, the vacuoles are as a rule bilaterally symme- 

 trical (Fig. 66, A) but, if the protoplasm is flowing very rapidly, the 

 vacuoles, while still retaining their attachment to the cell- wall, 

 become sloped in the direction in which the protoplasm is flowing 

 (Fig. 66, B) and thus altered in shape. This deformation of the 

 vacuoles is evidently due to the pressure of the stream of protoplasm. 



The pressure of the streaming protoplasm in a hypha of Pyronema 

 confluens is usually not sufficiently great to dislodge the vacuoles 



XTO 



sTwntr 



Fig. 66. — Pyronema confluens. Semi-diagrammatic drawing illustrating the effect 

 of pressure of streaming protoplasm on vacuoles. A, a highly vacuolated cell 

 in which the protoplasm is at rest or is moving very slowly. B, the same cell 

 in which the protoplasm is streaming rapidly ; the vacuoles, still attached to 

 the cell-wall, are being pressed out of their original shape by the streaming 

 protoplasm. The arrows indicate the direction of the stream. Each septum 

 has a central pore. Magnification, about 1000. 



from their attachment to the cell- wall. However, occasionally 

 vacuoles are so detached. One such vacuole was seen to be carried 

 in the streaming protoplasm to the nearest septum and to lodge 

 there on one side without passing through. This vacuole then 

 grew gradually smaller as if about to disappear altogether. It 

 seems probable that the detached vacuoles which float along in the 

 streaming protoplasm of Fimetaria flmicola and other ascomycetous 

 species gradually become reduced in size and that sometimes they 

 disappear altogether, but exact observations on the fate of floating 

 vacuoles have yet to be made. 



Causes of Streaming. — The causes of protoplasmic streaming 

 in septate mycelia, such as that of Pyronema confluens, appear to 

 be two : (1) vacuolar pressure and (2) increase in the amount of 

 protoplasm. 



