Discharge of Spores of Leptosphaeria acuta. 143 
that the spores have been forcibly ejected from the asci. In order 
to observe the process under the microscope, mature perithecia 
were carefully removed with the point of a scalpel (it is an advan¬ 
tage to remove a small piece of the wood of the stem below each 
perithecium at the same time, to ensure the base of the latter being 
uninjured) and affixed laterally to a cover-glass by means of a very 
minute drop of gum solution; the cover then being inverted over a 
drop of water contained in a deep cell cemented on a slide, the 
edges being sealed with vaseline. The perithecia can now be 
observed in profile under a fairly high power, and if the observer 
has sufficient patience the actual discharge of the spores through 
the ostiole will sooner or later be seen. The process is as follows. 
The tip of the gelatinous inner wall of an ascus appears 
through the ostiole (Fig. 6) and continues to elongate, sometimes 
slowly, but at other times rapidly, occasionally very rapidly, to a 
distance equal to 1 to 1£ spore-lengths above the aperture (Fig. 7). 
Usually 2 or 3 spores lying side are visible within the tube, the tip of 
the uppermost spore being pressed firmly against the extreme apex 
of the tube, the wall of which is here thinner than elsewhere, and, 
after the tube has elongated to the distance mentioned, bursts 
through the apex (Fig. 8), the spore being shot out through the 
pore with the speed of an arrow. Immediately the first spore has 
been discharged the tube suddenly contracts a short distance 
(very approximately equal to 5 //.), due, of course, to the pressure 
within it being slightly reduced by the ejection of the spore; how¬ 
ever, simultaneous with this short contraction the second spore is 
forced into and stops up the pore (Fig. 9) while the ascus elongates 
to about its original length. The second spore is forcibly shot out 
like the first, and the third spore pushed up into the pore immedi¬ 
ately afterwards, and so on until all the 8 spores have been ejected. 
After the discharge of each spore the tube always contracts a little, 
and the next spore is forced so rapidly into the place previously 
occupied by the spore just discharged, that the one seems to 
replace the other without any appreciable interval of time. After 
this contraction the ascus always elongates again nearly if not 
quite to its former length before the next spore is ejected. The 
spores are discharged in rapid succession, the time required for 
the discharge of the 8 spores of an ascus from the time the first 
spore is ejected to the shrinking of the empty gelatinous tube back 
through the ostiole, being usually only 4 or 5 seconds. Some¬ 
times the process is interrupted, 3 or 4 spores being discharged, and 
the tube then withdrawing into the perithecium to elongate and 
discharge the remainder later. The reason why the spores never 
