476 
Harper—Nuclear Phenomena in the Smuts. 
described the so-called copulation of the sporida, in which two 
cells become connected by a tube which joins them in pairs very 
much as are the conjugating cells of Spirogyra . DeBary 1 first 
pointed out the analogy between this union and the sexual fus¬ 
ions in the Conjugatae, and later 2 he presented the evidence 
more fully as to whether such fusions are sexual. As favoring 
this view he points out: First, the almost invariable occurrence 
of the pairing under the normal conditions of germination, i. e., 
germination in water. Second, the fusions are usually between 
two, and only two, sporidia. In the case of Tilletia, Entyloma , 
and Urocystis, when an odd number of sporidia are borne on the 
promycelium, the sporidia almost without exception fuse in 
pairs, and the odd one is left out and does not fuse with either 
of the adjacent pairs, although such a union would be very easy. 
This shows that a change has taken place in the fused pairs 
which makes a second union difficult or impossible. Most au¬ 
thors since DeBary’s earlier paper appeared, have accepted the 
view that the sporidial fusions are sexual unions. 
Brefeld 3 opposes this view and maintains that such fusing of 
cells is mere cell fusion in the sense in which Unger used the 
term. According to Brefeld the essential character in a sexual 
union of cells lies in the fact, that the conjugating gametes are 
incapable of further vegetative growth by division, but become 
capable of further development as a result of their union. He 
finds that the smut sporidia are capable of unlimited develop¬ 
ment without fusing so long as appropriate nutriment is sup¬ 
plied, and hence concludes that the fusions are purely vegeta¬ 
tive phenomena accompanying, perhaps resulting from, the star¬ 
vation of the sporidia. Such fusions are to be compared to the 
unions formed between the germ tubes of various spores or the 
hyphae of mycelia, such as will be described more fully below. 
Dangeard 4 has more recently studied the nuclear phenomena 
1 Beitr. Ser. V, pp. 126-127, and Morph. Phys., und Biol. d. Pilze, 
Mycetozoa, u. Bacteria, pp. 181-184. 
2 DeBary, Beitr. z. Morph, der Pilze, I, Ser., “ Protomyces and Phy- 
soderma.” 
3 Bot. Untersuchungen uber Hefenpilze, Hft. V. pp. 33, 49-50,175. 
4 Dangeard, ‘ ‘ Recherches histol. sur la famille des Ustilagin^es.” Le 
Botaniste, Ser. III., pp. 240, 268; and Le Botaniste, Ser. 4, p. 12. 
