196 Transactions British Mycological Soctety. 
species of Solorina contain cephalodia; that is an associated alga 
other than the normal gonidium. The intruding alga Nostoc sp. 
often becomes surrounded by the Solorina hyphae and a tubercle 
or cephalodium is formed which is referred to by the Moreaus 
as undoubted gall-structure. 
We understand by gall-structure an abnormal development of 
the plant affected, and due to the irritation of insect or fungus. 
It is as far as we know a purely vegetative development which 
never bears fruit, though the parasite causing the gall repro- 
duces freely. In the lichen thallus each symbiont fruits after 
its kind, and the fungus—the gall plant according to the 
Moreaus—fails to develop at all without the alga. 
A very curious instance of symbiosis between two fungi is 
described by Vainio (1921) as Mycosymbiosis. The association was 
discovered on the leaves of a tree from the Philippines. The 
first fungus to arrive, Gonidiomyces sociabilis gen. and sp. nov., 
somewhat resembles a Capnodium: it has stoutish branching 
septate mycelium of a dark brown colour: no fruits were found 
on it though presumably it is a member of the Pyrenomycetes. 
The second fungus, Diplothrix mirabilis, also new to science, has 
a fine gray mycelium. It lives on the hyphae of Gonidiomyces 
encircling them and finally producing Peziza-like apothecia. 
Neither fungus suffers from the association, though possibly 
Diplothrix gains most. The resultant growth resembles in form 
the lichen Strigula, also an epiphyte on leaves. 
MORPHOLOGY. 
A number of workers have selected certain groups and genera 
for detailed examination. Zanfrognini (1917) in a paper on the 
lichens of Somalia has added to the systematic description of 
the lichens an account of the structure of cortex and medulla 
in several species of Ramalina and Usnea. Shirley (1919) also 
approaches systematy by way of histological research. He has 
given much attention to the families Parmeliaceae and Stictaceae, 
studying cortices, rhizoids and more especially the pores that 
he finds present in the thalli; these latter occur in abundance, 
he finds, all over the thallus of P. tiliacea, minute openings 
difficult to see. In Parmelia limbata he has traced the pores or 
channels from just above the rhizoids to the upper surface 
where they show as shallow closed pits. He holds that these 
pores along with the cyphellae and other openings in the thallus 
of Stictaceae are not only for service in aeration, but allow water 
and food to be absorbed into the tissues. Shirley forgets the 
ready absorption of water by the thalline cortex, which water 
may or may not be charged with mineral salts. Relying on his 
interpretation of these structures, he would unite under Par- 
