Nuclear Phenomena in the Smuts. 
477 
in a number of forms and has come to some very interesting 
conclusions as to the sexual .reproduction of the group. He 
finds that in the genera investigated, Entyloma , JJstilago , and 
TJrocystis , the young spore contains two nuclei which later fuse 
so that the ripe spore contains a single nucleus. This fusion is 
considered as the equivalent of the conjugation of male and fe¬ 
male pronuclei and the smut spore as really an oospore formed 
in an oogone. On this ground Dangeard contends that the doc¬ 
trine of DeBary as to the sexual nature of the conidial fusions 
which occur later must be abandoned. In the germination of 
JJstilago in water the oospore nucleus passes into the germ tube 
and divides, cross partitions are formed, and a two, three or 
four celled promycelium results. In TJrocystis and Tilletia eight 
nuclei are regularly formed in the promycelium and pass into 
the sporidia which are apical in these forms. The nuclei show 
a membrane with double contour, a nucleole which is very large, 
and between the two a hyaloplasm more or less charged with 
chromatin. In the promycelia of Tilletia caries some figures 
were seen which suggested stages in the indirect division of the 
nuclei. Each sporidium contains normally one nucleus. The 
secondary sporidia contain two nuclei in Tilletia , indicating in 
them, as the author considers, a return to the condition of or¬ 
dinary vegetative cells. Dangeard observed the fusion of the 
sporidia of Tilletia in pairs and offers the suggestion, that in 
the passage of the nuclei from the promycelium to the spori¬ 
dia an unequal distribution of nuclei may occur, by which one 
sporidium may obtain two nuclei and another none at all. The 
fusion tubes then permit a re-establishment of equilibrium by 
the wandering of nuclei from the sporidia that have two nuclei 
into those that have none. He finds nuclei in the fusion tubes 
under conditions which suggest this view. 
DeBary proposed the term promycelium for the germ tube 
pushed out by the germinating smut spores, and I shall retain 
the term although Brefeld has introduced the word hemiba- 
sidium for the same structure in the effort to show a relation¬ 
ship between the Ustilagineae and the true Basidiomycetes. 
DeBary proposed also the term sporidium for the spores born 
on the promycelia. Brefeld very justly, however, points out 
