Nuclear Phenomena in the Smuts. 
491 
tubes which grow out from one branch and fuse at their ends 
with an adjacent branch. Such fusions are not to be considered 
as simply due to contact of two filaments that happen to cross 
each other’s path of growth. I have had abundant opportunity 
of observing the phenomenon in mycelia of Rhyparobius grown 
in a decoction of dung on the slide, and it is plain that many 
filaments cross and are in contact without fusing, while in other 
cases a branch will grow out in the shortest path possible to an 
adjacent branch and fuse with it. Sometimes two tubes grow 
out and meet and fuse at their tips just like the conjugating 
tubes of Spirogyra cells. The anastomosing is most common in 
the peripheral parts of a mycelium and may serve to secure an 
even distribution of food materials through the whole by a 
shorter route than would be otherwise possible. Certainly the 
mycelium is made a more definite unity by means of such anas¬ 
tomosing, but its advantage is by no means clear. 
Further examples are given by Woronin 1 and by Woronin and 
Nawaschin 2 of anastomosing in hyphae developed from the 
germinating conidia of the above mentioned Sclerotinia species 
when grown in plum juice. The young germ tubes, the older 
mycelial branches, and the germinating spores themselves may 
all become connected by fusion tubes which are developed in 
the greatest profusion without reference to the food supply or 
other noticeable external factors. 
Very recently the spore fusions in Protomyces macrosporus 
have been described and figured by C. M. L. Popta. 3 The 
spores fuse in this case soon after they have been expelled 
from the spore case and the formation of the fusion tube and 
the appearance of the fused pairs is very much the same as in 
the anther smut. In stained preparations of the spores before 
fusion four to seven nuclei are found, and after fusion also each 
cell of the pair shows from four to seven nuclei. The author 
concludes that there is no evidence that nuclear fusions follow 
the cell fusion and is apparently inclined to the opposite view. 
In living material highly refractive bodies were observed in 
1 Woronin, loc. eit., p. 11. 
5 Woronin u. Nawaschin, loc. cit., p. 10. 
8 “ Beitrage zur Kenntniss der Hemiasci,” Flora, Hft. 1, 1899. 
32 
