490 Harper—Nuclear Phenomena in the Smuts. 
relatively considerable distance before it reaches the appropri¬ 
ate subtratum for its further development. Whether the tube 
of a single spore would be incapable of reaching the ovary and 
producing the infection has not been determined experimen¬ 
tally, but it is plain that the certainty of infection taking place 
when once the spores are on the stigma is enhanced by the fu¬ 
sion process described. It would be interesting also to know 
whether the germ tubes are capable of drawing nutrition from 
the tissues of the style. The nuclear phenomena in connection 
with this fusion have not been studied, but in any case it 
cannot be considered as sexual in any sense of the word. 
It is a case of protoplasmic fusion where the advantage to be 
gained is simply the increased size of the resulting body. It 
belongs in the same category with the case of Nectria, and 
here the object, of the fusion is much more clearly indicated by 
the conditions under which it occurs. 
In two other related species of Sclerotinia the same process 
had been still earlier described by Woronin , 1 namely, in S. padi , 
whose spores fall on the stigma of Prunus padus and penetrate 
the host plant by means of a similar compound germ tube; and 
also in S. aucupariae parasitic on the mountain ash, which in¬ 
fects the berries of the latter by a compound germ tube from 
the stigma through the style. On the other hand, in S. megalo- 
spora which produces sclerotia in the fruits of V. idiginosum a 
single spore on the stigma can produce a germ tube long enough 
to reach the ovary and fusions of germ tubes in this species have 
not been observed . 2 The spores of this species of Sclerotinia are 
larger than those of the other three mentioned, but it would be 
hasty to assume that this visible difference in size is the direct 
cause of the difference in behavior of the species in germination. 
The length of the germ tube is not directly proportional to the 
visible size of the spores as can be shown in maqy cases. 
There are numerous accounts in the literature of the anasto¬ 
mosing of adjacent branches of a mycelium by means of 
1 Woronin, “ Die Sclerotienkrankheit der gemeinen Traubenkirsche und 
der Eberesche.” Mem. de VAcad. imp. des Sci. de St. Petershourg . 
1895; pp. 11-12, 17. 
2 Woronin u. Nawaschin, loc. cit., p. 11. 
