FUNGI.PYRENOMYCETES. 109 



which lives usually on dead but sometimes also on living plants. We know chiefly from 

 Woronin's researches into Sphaeria Lemaneae and Sordaria^ that in this case each 

 perithecium owes its origin to an archicarp and represents therefore a whole fructifica- 

 tion. But in other Pyrenomycetes, Xylaria for instance, a stroma is first developed on 

 the mycelium, a structure which may be cylindrical or pileus-like or cup-shaped 

 or branched and shrub-like, and is composed of compact and apparently homogeneous 

 tissue. In this structure numerous perithecia are afterwards formed. In such 

 cases, if retrogressive metamorphosis has not gone to such a length that archicarp 

 and antheridial branch are no longer to be seen in connection with the formation of 

 the sporocarp, it remains uncertain whether the stroma is merely a peculiar form of the 

 mycelium and sexual organs are formed in it which give rise to as many perithecia, or 

 whether the stroma itself is the product of a sexual act performed on the filamentous 

 mycelium and is to be regarded therefore as a fructification which subsequently forms 

 its asci in a number of perithecia ; the latter is the more probable alternative, since in 

 Claviceps the stroma comes from a sclerotium which is the product of a sexual act; 

 the sclerotia of Peziza however should be compared. 



The asexual reproductive cells, the gonidia, are produced in the Pyrenomycetes not 

 only from the mycelium but also and especially from the stroma, and in Penidllium 

 even from the wall of the perithecium. They are formed on longer or shorter hyphal 

 branches in large numbers, smaller and larger ones sometimes on the same species. 

 It was stated above that the receptacles known as pycnidia and spermogonia, which 

 also produce larger and smaller gonidia, are structures of varying significance ; they 

 sometimes belong to the species on which they appear, sometimes are parasitic. There 

 are in Fumago, as Zopf has shown, intermediate forms between gonidiophores and 

 pycnidia, and at the same time the formation of pycnidia in this case is instructive, 

 because it shows that they may be produced in different ways on the same species, 

 through true tissue-formation as well as by the interweaving of hyphae. 



The Fungus which produces the Ergot, Claviceps purpurea, may be chosen for a 

 more detailed description. Its growth begins with the formation of a filamentous 

 mycelium, which settles on the surface of the ovary of the Gramineae, especially of Rye, as 

 it lies enclosed between the paleae, covers it with a thick felt and penetrates into a part 

 of its tissue, sparing the apex and often other parts. N In this way a soft white felted 

 mycelium takes the place of the ovary and roughly retains its shape, the style being 

 often borne on the top. The surface of the hyphal tissue is marked by deep furrows 

 and forms an abundance of gonidia on basidia disposed radially ; the gonidia issue 

 forth from between the paleae imbedded in slimy matter. In this state the Fungus used to 

 be considered a distinct genus and was called Sphacelia. The gonidia may germinate 

 at once, and again give off gonidia by abstriction, and these, according to Kiihn, can 

 again at once produce sphacelia in other grass-flowers. When the formation of gonidia 

 is at its height the mycelium of the sphacelia forms at the bottom of the ovary a thick 

 belt of more compact hyphae, which is at first surrounded by the looser tissue of the 

 sphacelia ; this is the commencement of the sclerotium or ergot ; its outer surface 

 soon turns dark-violet, and it grows into a horn-shaped body which is often an inch long. 

 Meanwhile the sphacelia ceases to grow, its tissue dries up and is ruptured below by 

 the sclerotium and carried up on the apex of the latter, crowning it with a tall cap and 

 finally dropping off. The mature and hard sclerotium now remains in a state of rest 

 till the autumn and most frequently till the following spring, when the formation 

 of the fructifications begins if the sclerotium lies on moist ground (Fig. 67, A). The 

 stromata arise beneath the outer wall of the sclerotium by the formation of numerous 

 crowded branches at certain points on the central hyphae ; the tuft of branches bursts 

 through the wall and developes into a stroma consisting of a long stalk and a small 

 globular head. In the head are formed a number of flask- shaped perithecia (Fig. 

 67, ), which in this case have no bounding wall. Each perithecium is filled from the 

 bottom with many asci, in each of which several slender filiform spores (Fig. 67, D] are 



