CHAPTER III. SPORES OF FVNGI. 



95 



common in the Pyrenomycetes, but further investigation of individual cases is 

 desirable. 



The last remark specially applies to a considerable number of Pyrenomycetes, in 

 which the asci have the same structure as in Sphaeria Scirpi and S. Lemaneae and 

 elongate in the same way if they are placed singly in water when they are mature ; 

 among these are Sphaeria inquinans and S. obducens, Schm., Cucurbitaria Laburni, and 

 some species of Pleospora 1 . See Fig. 47. 



In ail these species the membrane of the ascus consists of a thin outer layer with 

 little power of swelling, and an inner soft gelatinous layer which swells to an unusual 

 extent in water. If a ripe ascus is placed in water, the inner layer swells and breaks 

 through the outer layer and protrudes in the 

 manner described in the case of Sphaeria 

 Scirpi. When the ascus is intact the inner 

 layer is thin as compared with the cavity 

 of the cell and appears to be tightly pressed 

 between the unyielding outer layer and the 

 protoplasmic utricle, which is tensely filled 

 with fluid contents. As soon as the pressure 

 upon it is relieved by the bursting of the 

 ascus, it swells to such an extent in the 

 direction of the longitudinal axis that the 

 lumen is contracted into a narrow canal and 

 the contents, whether spores or protoplasm, 

 are driven out through the fissure. This 

 happens in fully developed asci which are 

 nearly mature, and in young half-grown asci ; 

 in both the membrane in the uninjured state 

 is thin as compared with the wide lumen. 



In these species the ejection of the spores 

 is rare, though it has been observed ; the asci 

 when placed in water swell up at once, even 

 after elongation, into a clouded gelatinous 

 mass. This may be chiefly due to the fact 

 that the asci of these land species which swell 

 so readily have always been examined under 

 very injurious conditions, in sections, for in- 

 stance, or as crushed specimens suddenly 

 placed in water, and not in their normal state 

 a treatment which the asci of Sphaeria 

 Scirpi and S. Lemaneae which grow in water 

 would be better fitted to endure. But the 

 same remark applies also to other asci which 



do not suddenly elongate when isolated in water, as appears from the case of Cordy- 

 ceps ; these and many others when isolated and immersed in water show more or 

 less rapid gelatinous swelling of the walls of the asci. 



Some of the asci of which we are speaking have characteristic thickenings 

 on the apical portion of their walls ; in Cordyceps, Claviceps, and Epichloe typhina 

 the apex is thickened and becomes a nearly cylindrical body, almost as long as 

 the breadth of the ascus, pierced longitudinally by a very narrow canal, and set 

 like a lid or cork on the thin lateral wall. If we recall to mind the thickened apex 



FIG. 47. Pleospora htrbarum, Tul. (large form), a ripe 

 ascus fresh from the perithecium with compound pluri- 

 cellular spores, b the same after being placed in water, 

 the inner membrane being extended and the outer ruptured. 

 In this specimen the spores were ejected in the same way 

 as in Sphaeria Scirpi, but they usually remain in the 

 ascus in this species. Magn. 195 times. 



1 Tulasne, Carpol. 1. c. and II, t. XXVIII, &c. Currey in Microscop. Journal, Vol. IV, p. 198. 

 Sollmann in Bot. Ztg. 1863. 



