Discharge of Spores of Leptosphseria acuta. 145 
the outer at the apex is not quite clear; probably the outer firmer 
layer is somewhat thinner or weaker at this point. When the inner 
ayer has broken through and commenced to elongate its extreme 
tip can be seen to be much thinner than the wall of the tube 
elsewhere (Fig- 12) which is of very uniform thickness. Doubt¬ 
less this thinner apical part, through which the first spore 
is forced, is forshadowed by the thin apical region of the inner 
coat seen in the young ascus. The thickened upper part of 
the inner coat also seen at this young stage seems to be a reserve 
piece of thickening destined ultimately to be extended when the 
tube elongates, as suggested by de Bary, although the whole inner 
wall is capable of stretching to a considerable extent. After dis¬ 
charging its spores the gelatinous tube collapses and shrinks back 
considerably, and, if in water, its wall becomes greatly swollen 
(Fig. 14). 
Fig. 10. Tip of very young ascus. Fig. 11. Tip of mature ascus. 
Fig. 12. Apex of elongated inner ascus wall before first spore has been 
ejected, showing the thinner apical part of wall. Fig. 13. The same with 
the first spore breaking through the apex. Fig. 14. Tip of empty and 
collapsed inner ascus wall showing the apical pore and greatly swollen wall. 
Fig. 15. 8pore germinating in moist air. 
Figs. 10, 11 and 14, X 500 ; Figs. 12 and 13, X 1200; Figs. 15, X 400. 
The account given above for Leptosphceria acuta is exactly 
the same as described by Pringsheim 1 for Sphceria Scirpi 
(—Pleospora scirpicola), which occurs on decaying submerged parts 
of stems of Scirpus lacnstris. Here the inner gelatinous coat of 
the ripe ascus suddenly breaks through the apex of the outer 
cuticular layer and elongates in a few seconds to about three times 
the length of the original ascus; the spores being shot out success- 
1 Pringsheim, Jahrb. wiss. Bot, Bd. 1, 1858, p. 189 ; or see de Bary, 
loc. cit, p. 93. 
