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SPORE DISSEMINATION 27 
often happens that the perithecia are empty or contain but few 
loose spores. The transformation of the perithecium to the 
latter condition has been repeatedly observed in cultures. P. de- 
cipens, P. vestita, and P. zygospora are especially favorable species 
for illustrating this point. If the cultures are kept in suitable con- 
dition for the development of the plants, they will continue grow- 
ing for a long time but will finally all die, when there may be 
found among the debris many perithecia with no spores at all in 
them. Usually there are, however, a few found, but only a few in 
any case. In such cases the paraphyses have all disappeared also. 
It is in younger stages when the vitality is just beginning to wane 
that the paraphyses appear abundant. Later, like all the remainder 
of the more delicate tissue of the perithecium, they deliquesce. 
They also become very numerous when the cultures dry gradually. 
Returning again to the stretching asci, there are several im- 
portant points to be considered in connection with them. Zopf * 
first called attention to the fact that but one ascus ruptures at a 
time. In observations of certainly not less than a hundred peri- 
thecia of the P. curvula group, no deviation from this rule has ever 
been observed. They may be found at all elevations up to the 
very narrow neck of the perithecium, but as soon as one ascus 
ruptures another takes its place in regular succession and there 
never appears to be any confusion regarding which shall precede. 
Even in this genus, however, the machinery sometimes becomes 
clogged for some reason and the spores are simply pushed out of 
the ostiolum forming a globular mass on the beak. But this 
phenomenon is much less common in this genus than in some of 
the others. 
The frequency with which the asci erupt, according to my 
observations, varies greatly in perithecia treated exactly alike. 
Observations on this point have been made especially with P. 
minuta and P. curvula. The first extended observation was made 
on the fourth of November, 1899, with P. minuta. Perithecia 
were carefully removed from the substratum with needles, mounted 
in a drop of water and covered with a thin, light cover-slip. After 
several mounts were made one was obtained which appeared to be 
in just the right condition for study. This was allowed to eject 
* Zeitschrift gesammt. Naturwissen. (Halle), 56. 1883. 
