(121) 
MELIOLASTEE, A NEW GENUS OF THE MICEO- 
THYEIACEAE. 
By Ethel M. Doidge. 
(Read August 21, 1918.) 
As a result of the work of re-examination and revision of certain ascomy- 
cetes carried out in recent years by v. Holinel and Tlieissen, the group 
formerly known as the Perisporiales"'" has been entirely reorganised. It was 
laid down by v. Hohnelf that only species showing the so-called "inverse- 
radial " structure of the perithecium should be included in the Micro- 
thyriaceae ; a number of species with hemispherical perithecia but not 
showing this typical structure were thus excluded, and for these Theissen 
constituted the families Hemis])Jiaer{aceaeX and Tricho])eUaceae,^ the latter 
group consisting of forms with a thallus-like structure, and with fruiting 
bodies formed " pycnotically " in the thallus. The three families, Micro- 
thyriaceae, Hemisj^haeriaceae and Trichoj^eltaceae, constitute the group 
Hemis'phaeriales, and are thus contrasted with forms having spherical 
perithecia like the Perisporiaceae. In both groups certain genera, e. g. 
Meliola and Asterina, bear hypliopodia at regular intervals on the mycelium ; 
the division into families is based onlv on the structure of the fruitino- 
bodies, but mycelial characters are often used as generic distinctions. 
This being the case it is interesting to find amongst fungi occurring in 
South African forests, species which appear to be intermediate in character, 
and in which are combined peculiarities of more than one family. The 
vegetative stage of the Tricliopeltaceae consists of a flat ribbon or disc 
formed by the repeated branching of the constituent hyphae, which are fused 
by their lateral walls ; the " pycnothecia," as the fruiting bodies are called, 
are hemispherical, and are formed in the vegetative membrane by the 
thickening of certain portions of it. This group thus forms a very complete 
contrast to fungi like the Meliolas which have a filamentous, spreading 
mycelium, and spherical perithecia which are quite a distinct development 
from the vegetative mycelium. 
* Englev, ' Die Pflanzenfaiiiilien.' 
t V. Hohnel, ' Fragm. z. Mijk.,' x, p. 13, ff. 
X Theissen, ' Ann. Myc.,' xi (1913). 
§ Theissen, ' Mycologische Centralb.,' iii, No. 6, pp. 273-286. 
