CYTOLOGY OF EOCRONARTIUM MUSCICOLA 
411 
and the resulting fusion nucleus then increases rapidly in size. Later 
it divides, and the daughter nuclei migrate toward the ends of the now 
much elongated basidium. A transverse septum is then laid down. 
Subsequently these nuclei also divide and other septa are formed, 
the basidium being finally composed of four superimposed, uninucleate 
cells. From each cell a sterigma is then put out, and at its tip a spore 
begins to form. The spore after reaching maturity germinates in the 
uninucleate condition. In germination a secondary spore is developed, 
and the nucleus migrates into this. The germination of this secondary 
spore was not watched, and no later stages showing germ-tubes con- 
taining more than one nucleus were obtained. The nuclear divisions 
in the basidium were not actually observed, and no details of nuclear 
structures are figured or described. Branching, septate paraphyses 
composed of binucleate cells lie between the basidia. Sappin-Trouffy 
points out the resemblance between the transversely septate basidium 
of Auricularia and the internal promycelium of Coleosporium, but he 
lays little emphasis upon the point, and considers the basidium homol- 
ogous with the oospore. 
Juel (25), from the examination of another species, Auriailaria 
mesenterica, gives a detailed account of the nuclear divisions in the 
basidium, but adds nothing to the knowledge of the nuclear history 
in this genus. He states that the fusion nucleus lies at the center of 
the cylindrical basidium and is of an elongated shape due to the 
narrowness of the cell. It contains an evident nucleolus and a delicate 
chromatin network. Without leaving its central position it under- 
goes mitosis, the nuclear membrane disappearing and the spindle 
lying parallel to the long axis of the basidium. Delicate astral rays 
may be seen at each pole radiating into the cytoplasm from a deeply 
staining point which seems to be a centrosome. On the spindle there 
are six or eight deep-staining bodies which Juel regards as chromosomes. 
In the second division in the basidium the spindles are smaller and 
stouter, and lie within a well defined nuclear membrane. They are 
in all other respects similar to the spindle of the first division, and re- 
semble it in lying parallel to the long axis of the cell. Juel advances 
the theory that the Basidiomycetes are phylogenetically of two groups, 
"the Protobasidiomycetes (Uredinales, Auriculariales, and Dacryo- 
mycetales) and the Autobasidiomycetes (Tremellales and Hymenomy- 
ce tales)," in the former the spindle lying parallel to the long axis of 
the basidium, and in the latter at right angles to it. 
