80 RESEARCHES ON FUNGI 



stolonifer are about 26° C. and 10°- 12° C. respectively, and for 

 Phycomyces nitens 28° C. and 13°-15° C. respectively. Injuries 

 influence streaming adversely : they cause a sudden outflow of 

 protoplasm at the point of injury and a cessation of streaming for a 

 long time or altogether. Streaming continues to take place slowly 

 at an air pressure of 10 mm., and therefore at a very low partial 

 pressure of oxygen. 



In a discussion of the biological significance of streaming, 

 Schroter makes the following remarks. Streaming at first is 

 acropetal and with short breaks continues so for some time. In 

 this way material is transported to the ends of the hyphae. The 

 most rapid growth takes place during acropetal streaming, less 

 rapid growth whilst the protoplasm is at rest, and no growth during 

 basipetal streaming. In a mature mycelium the protoplasm flows 

 into the developing sporangiophores and, finally, into the sporangia 

 where it is used in the formation of the spores. In Mucor stolonifer, 

 streaming ceases first of all in the hyphae of the mycelium, then in 

 the stolons and, lastly, in the sporangiophores. We thus see that 

 Schroter, like de Vries and Arthur, regarded streaming as an 

 important means of transferring material to points of growth. 



In 1911, Raybaud, 1 in a long memoir, gave an account of the 

 influence on the form and mode of growth of Phycomyces nitens and 

 Rhizopus nigricans exerted by ordinary light, ultraviolet radiations, 

 temperature, pressure, the hygrometric state of the air, osmosis, 

 transpiration, and the acidity or alkalinity of the nutritive sub- 

 stratum, in the course of which he added the following facts, among 

 others, to our knowledge of the movement of protoplasm within the 

 hyphae. A germinating spore which in the dark has swollen up 

 and is about to emit a germ-tube, if suddenly subjected to bright 

 light, may be killed ; but, if the spore has put out a germ-tube, 

 sudden exposure to light does not kill the plant but causes the 

 protoplasm to contract and flow toward the spore. If a mycelium, 

 grown in the dark, is suddenly exposed to light, the protoplasm 

 flows basipetally from the ends of the hyphae filled with homo- 

 geneous protoplasm toward the more vacuolated parts of the 



1 L. Raybaud, " Influence du milieu sur les Mucorinees," Annates de la Faculte 

 des Sciences de Marseille, T. XX, 1911, pp. 1-248, PI. I-V. 



