204 



slightly toothed, remaining often very visible, as in P. tubcrosa, P. rapulum, and 

 P. cchinophila ; but sometimes also closing together, so that in order to distin- 

 guish the opening, it is necessary to prove its existence by squeezing the thin 

 walls of the ascus together, as in the small Mollisia, Mitrula, &c. Most fre- 

 quently, the extremity of the ascus presents a broad truncated nipper, very thin 

 in the centre. 



The species of this section frequently have sporidia vi^ith a tendency to divi- 

 sion, or they are clearly divided ; and very often they are simple, but become 

 divided at the time of germination. I know of none that are verrucose or areolate; 

 they are rarely spheerical, but most frequently fusiform, more or less elongated, 

 and sometimes club-shaped ; many are more or less curved, and in general they 

 are much smaller than those of the species in the first section. The consistence 

 of the cup is more firm and elastic, and much less waxy ; the hairs when they 

 exist have a different appearance. The species are rarely terrestrial, being much 

 oftener found on dead wood, dead leaves and stems, and sometimes even on the 

 living branches. This second division includes Geoglossum, Mitrula, Leotia, 

 Phialea, Helotium, Lachndla, Mollisia, and all the genera belonging to them. 



There exists a little group of ascigerous fungi in which the mode of dehis- 

 cence is not yet well knovim : I allude to the true Tuberaceae, Tuber, Elaphomyces, 

 and others, that is in fungi completely closed, in which the asci are altogether 

 internal, and cannot discharge their sporidia externally. I think that in this 

 group the asci do not open, but disappear insensibly by absorption, and thus leave 

 their sporidia free. This group, altogether natural and distinct, certainly belongs 

 to the Ascomycetes, but should not be placed in the Discomycetes, from which 

 they differ notably. I may say the same of the Pyrenomycetes in which the 

 greater part of the species probably have dehiscent asci, but this family, in which 

 the processes are most difficult to observe, does not come within the limits to 

 which I confine myself. 



It will be seen from what I have said, how much importance I attach to the 

 mode of dehiscence, and it is with the view of inducing mycologists to observe it 

 more carefully, that I have dwelt upon it. There is no great difficulty in observ- 

 ing it, a magnifying power of 300 diameters is sufficient, but it is necessary to 

 search for it at the upper extremity of the open asci. These asci are always to be 

 recognised by the absence of protoplasm, by which they differ from the young 

 plants which have not yet formed their sporidia. Moreover, the tincture of iodine 

 may be employed, which colours the membrane and renders the operculum more 

 visible. This tincture should, indeed, always be employed in the examination of 

 species, because it often gives a deep blue colour at the extremity of the ascus, as 

 in Aleuria proper, P. cochleata, P. badia, P. vesiculosa, and others, and the char- 

 acter has a certain value ; in other cases the colour is fainter, as in P. firnia, P. 

 cchinophila, &c. ; in other cases again, only the extreme margin of the opening is 

 tinted, as in Mitrula, or it appears as a blue point, while more frequently the 

 iodine does not cause any other colouration than a yellowish tint to be produced. 



