THE TRANSLOCATION OF PROTOPLASM 123 



(1) Vacuolar pressure. — As we have seen, Charlotte Ternetz, 

 as a result of her investigations on Ascophanus carneus, came to the 

 conclusion that the movement of protoplasm in the hyphae of that 

 Discomycete is due to differences of osmotic pressure in the cells of 

 the hyphae. My own observations on Pyronema confluens, Fimetaria 

 fimicola, Rhizoctonia solani, etc., support the idea that osmotic 

 pressure is a main cause of the flowing of protoplasm in septate 

 mycelia, although not the only cause. The ultimate hyphae from 

 which protoplasm is flowing away (cf. A in Fig. 63, p. 116) have all 

 ceased to grow and have enlarging vacuoles. In every cell of such 

 ultimate hyphae the protoplasm may be divided into two classes : 

 (I) fixed protoplasm which, as an extremely thin non-granular clear 

 layer, lines the cell- wall and surrounds each vacuole ; and (2) movable 

 protoplasm which, in the form of a granular mass, is enclosed by the 

 fixed protoplasm. At first a cell is full of protoplasm. As it ceases 

 to grow in length, vacuoles attached to the cell- walls appear in it 

 and grow in size (cf. Fig. 63, E, D, C, and B, p. 116). Then the 

 vacuoles may cease to grow and the cell may serve as a channel for 

 the transportation of protoplasm (Fig. 63, B). Subsequently, the 

 vacuoles may begin to grow again and the cell may lose all its labile 

 protoplasm and, finally, die of exhaustion. The emission of proto- 

 plasm from a cell can be readily accounted for by supposing that 

 the pressure required for the process arises in the vacuoles. If, through 

 the addition of a soluble salt or other osmotic substance to the cell- 

 sap, the osmotic pressure of the sap is increased, the vacuoles will 

 press against the mobile granular protoplasm and this, unable to 

 escape through the thin layer of clear fixed protoplasm lining the 

 outer cylindrical cell-wall, must flow in the direction of least resist- 

 ance, namely, through the pore of an adjacent septum and onwards 

 toward younger growing hyphae, in which, presumably, the pressure 

 on the granular protoplasm is much lower. Thus enlarging vacuoles 

 drive the protoplasm out of certain hyphae which have ceased to 

 grow into hyphae whose ends are full of protoplasm but are growing 

 rapidly in length and so are making room for the protoplasm that 

 is flowing into them. 



(2) Increase in the amount of protoplasm. — In a young mycelium 

 growing in a fresh culture medium the total amount of protoplasm 



