THE TRANSLOCATION OF PROTOPLASM 113 



Hanging-drop Cultures. — Cultures of the mycelium of Pyronema 

 confluens suitable for studying the streaming of the protoplasm 

 through the hyphae were prepared as follows. Some fruit -bodies 

 of the fungus, together with underlying soil, obtained from pots at 

 the Dominion Rust Research Laboratory, were placed in closed 

 Petri dishes and left there for a few hours. A van-Tieghem cell was 

 then set up in the usual way : a glass ring was fixed to a slide with 

 paraffin wax, a little water was poured into the cell, and vaseline 

 was smeared over the upper surface of the ring. A drop of cleared 

 dung-agar was now spread on the under surface of a sterilised cover- 

 glass, the cover was removed from the Petri dish, and the cover-glass 

 was held over a group of the fruit -bodies. Immediately some of 

 the fruit-bodies puffed and thereby shot up a few spores into the 

 hanging drop of dung-agar. The cover-glass was then set on the 

 van-Tieghem cell. Thus the spores were sown without being handled 

 by any instrument. 



Growth of the Mycelium and Development of Vacuoles. — The 

 spores of Pyronema confluens are oval and colourless (Fig. 62, A). 

 After having been sown, they began to germinate in about four and 

 a half hours (B), and in fifteen hours each spore had given rise to a 

 rapidly growing, branched, septate mycelium (C). The spores before 

 germination are filled with protoplasm, but small rounded vacuoles 

 appear within them as they swell up and put out germ-tubes (c/. A 

 and B). In a young mycelium, the younger hyphae are completely 

 filled with protoplasm, but small rounded vacuoles develop in all the 

 cells as these become older (C). As growth continues, the older 

 cells and the younger hyphae which have ceased to grow in length 

 become more and more vacuolated (c/. C and E with D, F, G, H), 

 so that it is evident that in some way they lose a considerable 

 amount of protoplasm. 



Protoplasmic Streaming. — If a spore of Pyronema confluens 

 germinates on one side of a hanging drop, the mycelium, within 

 about twenty-four hours, spreads across the drop as a vigorous 

 but somewhat sparsely-branched structure. In the middle of the 

 drop in such a young mycelium there are leading radiat- 

 ing hyphae, like those shown at B in Fig. 63, composed of 

 chains of cells, and in these hyphae the protoplasm may be 



VOL. v. I 



