THE TRANSLOCATION OF PROTOPLASM 



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in transpiration. If dry air is passed rapidly over the mycelium 

 streaming ends with the collapse of some 

 hyphae and the bursting of a number of 

 other hyphae. The local application of 

 solutions of cane-sugar, potassium nitrate, 

 etc., causes a streaming of protoplasm 

 toward the place of application. Repeated 

 change of direction of streaming in a hypha 

 can be caused by appropriate local appli- 

 cations of a sugar solution. Protoplasmic 

 streaming in Mucor stolonifer and Phyco- 

 myces nitens is in the main a to-and-fro 

 flowing of the whole of the protoplasm. 

 It should be called neither rotation nor 

 circulation ; it rather resembles the mass- 

 translocation of protoplasm in the Plas- 

 modium of the Mycetozoa. Sometimes, 

 while the central protoplasm, vacuoles, 

 and cell-sap, in the form of a central 

 cylinder, are moving forward, an outer 

 mass of protoplasm, free from vacuoles, 

 in the form of a cylinder-mantle, is moving 

 basipetally (cf. Fig. 46, B). Whilst light, 

 in general, has but little influence on the 

 movement of the protoplasm, after the 

 mycelium has been in the dark sudden 

 exposure to light may initiate or hasten 

 streaming. Changes of temperature affect 

 streaming in the same manner as they do 

 in Phanerogams. A rise of temperature 

 hastens streaming or, if the protoplasm is 

 at rest, may cause streaming to begin. 

 Cooling may cause streaming to cease. 

 Too high a temperature results in a 

 backward streaming, and at about 55° C. 

 streaming ceases and the mycelium dies. 

 The optimum and minimum temperatures for streaming for Mucor 



Fig. 46. — Rhizopus ni- 

 gricans. Protoplasmic 

 streaming in mycelial 

 hyphae. A, a long 

 vacuole is pushing 

 forward into dense 

 protoplasm, followed 

 by highly vacuolated 

 protoplasm. B, a hy- 

 pha in which the 

 protoplasm is flowing 

 in opposite directions 

 at the same time. 

 There is a broad vac- 

 uolated axial stream 

 of protoplasm and a 

 sheath-like peripheral 

 return-current of non- 

 vacuolated proto- 

 plasm. Copied by the 

 author in black-and- 

 white from Arthur's 

 pencil drawing in his 

 The Movement of Pro- 

 toplasm in Coenocytic 

 Hyphae. 



