86 DIVISION I,—GENERAL MORPHOLOGY. 
Zopf the uppermost spore in some Sordarieae is even attached to an inwardly directed 
process from the membrane at the apex of the ascus. No such arrangements have 
been observed in the majority of cases, and the apical position of the spores is 
sufficiently explained by the consideration that the one-sided expansion of the apical 
region must produce currents in the contained fluid in the direction of the apex, 
which must push the spores suspended in it towards this expanding apex. 
When the wall has reached a fixed maximum of extension, it suddenly gives 
way at a point of least cohesion near the apex, which is the poznt of dehiscence; at 
the same moment the elastic lateral wall contracts to the size spoken of above as the 
original size, and the apical portion of the fluid contents together with the group 
of spores is driven out through the fissure. Then the open ascus collapses and 
perishes. 
The arrangement of the spores in the apical portion of the ascus before their 
ejection, when there are no special arrangements for attaching and securing them, is 
evidently the result of the conditions of space and form. In many Discomycetes for 
instance the spores are ellipsoidal or elongated, and their length greater than the 
breadth of the ascus ; they lie therefore parallel in the ascus, in a single longitudinal 
row close behind one another, each placed obliquely and touching the wall of the 
ascus with both ends, the uppermost one having its upper extremity close to the apex 
(Figs. 39 w and 43). Ifthe breadth of the ascus is much greater than the diameter 
of the spores the arrangement is more irregular; thus there is an irregular longitudinal 
row in Ascobolus pulcherrimus', two such rows in many Ascoboli”? (Fig. 45), and an 
irregular ball crowded up into the apex of the ascus in the eight-spored asci of 
Exoascus Pruni® and in the many-spored asci of Ryparobius“. But the longitudinal 
arrangement is maintained in the comparatively very broad asci of Sordaria (Fig. 44), 
where it may be due to the attachment.of the spores to one another. 
The form of the fissure varies with the species, and it cannot always be distin- 
guished with certainty. 
A longtitudinal rent simple or lobed, passing over the apex and leaving a broad 
hole when the ascus is emptied, forms the opening in the asci of Exoascus Pruni, 
Peziza cupularis and Erysiphe®, and according to Boudier * of Geoglossum, Helotium, 
Leotia, and Bulgaria sarcoides. 
In many Pezizas, as P. convexula, P. confluens, P. granulata, P. abietina, 
P. vesiculosa, P. melaena, all the Ascoboli and Helvella crispa, the fissure is annular 
and runs close beneath the blunt summit of the wall of the ascus, which is therefore cut 
off like a lid, and when the spores are ejected is lifted off either all the way round or 
only on one side where the uppermost spore touches the wall of the ascus; the 
latter is the case, for instance, in Peziza vesiculosa and P. granulata. In larger 
Ascoboli the edge of the lid may be seen before the ejection of the spores as a 
distinctly marked transverse line”. In some forms, as P. abietina and P. vesiculosa, 

1 Woronin, Beitr. II, t. III. 
2 Boudier in Ann. d. sc. nat. ser. 5, X. 
3 De Bary, Beitr. I, t. III. 
* Bondier, 1. c. 
5 R. Wolff, Erysiphe ; see the literature cited in section LXXIV. 
® Loc. cit. p. 202. 7 See Boudier’s figures, 1. c. 
