Nuclear Phenomena in the Smuts. 
489 
The case described by Osterhout 1 of the combination of the 
four tetraspores of Rhabdonia in their germination to form a 
single vegetative body may perhaps be placed in this same cate¬ 
gory, although the tetraspores do not actually fuse. 
A much more striking case of fusion of germ tubes where no 
strictly sexual significance in the phenomenon is possible, has 
been worked but by Woronin and Nawaschin. 2 The case is that 
of Sclerotinia heteroica, which is a heteroecious ascomycete pro¬ 
ducing conidia on Vaccinium uliginosum and sclerotia in the 
fruits of Ledum palustre. The ascospores of the fungus infect 
the leaves of Vaccinium uliginosum and produce a mycelium 
which develops a rich, conidial fructification. The conidia 
from the leaves of the Vaccinium fall on the stigmas of the flow¬ 
ers of Ledum palustre at the time of anthesis, the germ tube 
penetrates the whole length of the style and develops a mycel¬ 
ium in the ovary. As the latter grows, it is mummified by the 
mycelium and becomes a sclerotium, which passes the winter in 
a resting condition and in the following May germinates and 
produces a long stalked peziza cup. The asci of this peziza dis¬ 
charge their spores in the air and they are carried to the 
young leaves of V. uliginosum , infecting them and pToducing 
again the conidial fructification. The peculiar fusions referred 
to occur in the infection of the ovary by the conidia through 
the stigma. The authors find that a number of the conidia 
which have fallen on the stigma combine their germ tubes by 
fusion in order to penetrate through the style to the ovary with 
its abundant food material below. The conidia lie on the stig¬ 
ma like pollen grains and several, as many as five or six, push 
out germ tubes which, instead of growing independently down¬ 
ward into the subtratum, converge towards each other, prob¬ 
ably by means of mutual chemotactic stimulation, and become 
fused into a single larger tube which then proceeds downward 
through the style. Here we have very plainly a fusion of in¬ 
dividual cells with loss of their independence for the sake of 
producing a larger body, a larger germ tube, for traversing the 
1 Osterhout (W. J. V.), Annals of Botany, 1896. 
2 Sclerotinia heteroica Zeitschr.f. Pflanzenkrankheiten, Hft. 3 u. 4, 
1896. 
