180 Transactions British Mycological Society. 
listed the name without description, in Chloris Lugdunensis, 
1785). The genus Hysterium was considered in a broad sense 
by Persoon, and subsequent workers, especially upon examining 
the spores, placed certain of the species in other genera. Certain 
species of Xyloma as described by Persoon were also subse- 
quently removed to the Hysteriales. Species of Acrospermum 
were placed by Persoon in the genus Clavaria. In Mycologia 
Europaea (21, p. 331) Persoon described Tryblidium. 
Persoon brought together a number of similar fungi into the 
genus Hysterium, and made a considerable advance in systema- 
tizing the knowledge concerning certain forms which had pre- 
viously been overlooked or placed in the lichens or in various 
genera of fungi. The workers up to, and even including, 
Persoon, had naturally not been able to make much headway 
with these fungi, since the internal, microscopic characters were 
still almost unknown. Rapid progress was soon made and it is 
unnecessary to attempt to follow the specific, or even later 
generic, changes that came to be made, but the systems of 
classification and development of knowledge may be followed 
in a general way. 
Sowerby (22) illustrated and gave notes on several forms. 
Albertini and Schweinitz (23) followed Persoon. 
De Candolle (24, p. 280) gave the name “ Hypoxyla”’ to a group 
of genera including Sphaeria, Xyloma, Opegrapha, Verrucaria, 
Hysterium and Hypoderma. This last genus was described as 
new, for subepidermal Hysteria, and five species of Hysterium 
were transferred to it. 
Muehlenberg (25, p. ror) listed Glonium stellare without descrip- 
tion. The genus was later described by him in Fries (27). Nees 
(26, Ueberblick, pp. 72-86) included Antennaria, Hysterium, Sphaeria, 
Thelobolus and Nemaspora in his group Myelomyci (Kern- 
schwamme). 
Fries (27) in his Systema Mycologicum proposed the name 
Pyrenomycetes, with Xylomyci Willdenow, Sclerocarpi Per- 
soon, Hypoxyla De Candolle, and Goniomyci and Myelomyci 
Nees, as synonyms. He included as orders Phacidiacei, Sphaeri- 
acel, Cytisporei, and Xylomacei, but noted that the Phacidiacei 
were aberrant in that they were often cupulate, but had the 
general habit of Pyrenomycetes. Under the Phacidiacei he in- 
cluded Hysterium Tode (including Hypoderma DC.) with forty- 
eight good species, three more doubtful, four listed as aberrant, 
and some twenty other species were transferred, discarded, or 
noted; Glonium (under Muehlenberg’s name) with G. stellatum: 
Actidium with two species; and the genera Rhytisma, Phacidium 
and Excipula. Lophium he included under Sphaeriacei. Acro- 
spermum was placed in the Sclerotiacei of the Gasteromycetes. 
