1 28 Wormald. — On the Occurrence in Britain of the 
Microscopic examination of an apothecium which is liberating spores 
shows that when the ascospores are fully developed they are situated in the 
upper half of the ascus, at first in a single row (monostichous) and usually 
with their long axes oblique to the axis of the ascus, but shortly before they 
are expelled they become more or less distichous nearer the apex of the 
ascus, which meanwhile increases in size and becomes vacuolate, a single 
vacuole finally extending from the apex almost to the base. After dis- 
charging its spores the ascus contracts, and its wall shows minute striae ; an 
ascus which measured 19a xi2ju immediately before its spores were set free 
contracted to 162 x 9 fi after dehiscence (Fig. 5, d and e). 
The ascospores are non-septate (a few spores with a single median 
septum were seen on one occasion), variable in size and shape, usually 
irregularly ovoid, some broadly ovoid, others elongate, sometimes flattened 
on one side ; the ends are generally rounded, but often narrowed and almost 
pointed, occasionally one end mucronate (Fig. 7). 
Paraphyses are present ; they are approximately the same length 
as the asci before the latter elongate to discharge their spores, 2-2*5 /u 
in diameter, and are either simple or bear from one to three branches ; they 
are usually very slightly dilated towards the apex, but in some cases the tip 
was distinctly swollen (Fig. 6). 
Since the dimensions of asci and ascospores are usually quoted as 
characters of primary importance in distinguishing the apothecial forms 
found on stone-fruit, careful measurements were made of asci and ascospores 
of three of the apothecia found on plums and the ascospores of a fourth. 
The first apothecium examined was probably not quite mature, for although 
the spores were fully formed in many of the asci and were readily set free 
on tearing out a portion of the hymenium in water, no asci with distichous 
spores (as seen later in older specimens) were observed ; the second and 
third had asci with monostichous and others with distichous spores, as well 
as a number which had discharged their spores, while the fourth apothecium 
had become dry after reaching maturity, and when examined, after soaking 
in water, the asci were found to be disintegrated, though numerous spores 
were to be obtained. 
The results obtained are given in the following table : 
Dimensions of the Asci of the Plum Sclerotinta. 
Asci with monostichous spores. Asci with distichous spores. 
Apothe- Number of asci 
cium. measured. 
Range of variation. 
Average 
size . 
A T umber of asci 
measured. 
Range of variation. 
A verage 
size. 
No. 1 
2 5 
124-163 x 7.5-10.5 
143.6 x 8.8 
None present 
. — 
— 
2 25 
1 28-170 x 8.0-10-0 
151-0 x 8.9 
10 
164-198 x 1 1-13-5 
184.4 x I2 * 
3 
2 5 
150-188 x 7-5— 9*5 
i68.o x 8.4 
30 
162-226 x IO-I2.5 
194.6 x 10. 
Result 
75 
1.24-188 x7’-5-i 0.5 
153.4x8-7 
40 
162-226x10-13.5 
192-0 XII" 
