146 



RESEARCHES ON FUNGI 



by van Tieghem ^ and subsequently confirmed by Brefeld,^ the 

 myxamoebae, derived from spores, at first wander about and feed 

 and multiply themselves by fission separately (Fig. 82, E and F). 



Then all the units come 

 together and form an 

 aggregate plasmodium 

 in which the indi- 

 vidual myxamoebae 

 retain their individu- 

 aUty (Fig. 82, G, H, 

 and I). Finally, the 

 aggregate plasmodium 

 builds up a long, sterile, 

 cellular stalk crowned 

 by a globular mass of 

 spores (Fig. 82, J). 

 The stalk-forming 

 myxamoebae, on be- 

 coming transformed 

 into stalk-cells, are 

 thereby immobilised 

 and rendered incap- 

 able of reproducing the 

 species ; nevertheless, 

 they contribute to the 

 weKare of the other 

 myxamoebae — those 

 which eventually form 

 the spores — by con- 

 structing an apparatus 

 up which the Tatter may ascend from the substratum to take up a 

 position which presumably is favourable for spore-dispersion.^ 



^ Ph. van Tieghem, " Sur quelques Myxomycetes a plasmode agrdg6," Bull. 

 Soc. Bot. France, T. XXVII, 1880, p. 317. 



2 0. Brefeld, Untersuchungen iiher Pilze, Leipzig, Heft VI, 1884. 



^ Dictyostelium mucoroides often appears on old horse-dung cultures at Winnipeg. 

 The communal activities of the myxamoebae illustrated in Fig. 82 were observed 

 in artificial cultures. 



Fig. 79. — A, C, and D, Volvox aureus. Described by 

 West and others as a colony of cells, but regarded 

 by the author as an individual plant. A, a 

 " monoecious sexual colony " (West), from Raw- 

 cliffe Common, Yorkshire, England : a, andro- 

 gonidia ; g, gynogonidia ; the other cells all 

 vegetative and united by protoplasmic processes. 

 C, two antherozoids. D, a ripe oospore. B, a 

 ripe oospore of V. globator. From G. S. West's 

 British Freshwater Algae (1904). Magnification: 

 A, 210 ; B and D, 475. 



