198 Transactions British Mycological Socvety. 
two others indeterminable) as swollen tips of the hyphae, as 
clusters of sphaeroid cells, as solitary inflated filaments or in 
strands of hyphae. These oil cells were more abundant in the 
quicker growing species and in regions of special growth. 
In his paper on Graphidaceae, Bioret (1921) finds that the 
elliptic contour of the thallus in numerous species depends on 
the form of the bark cells of the host tree, as these elongate 
transversely so does the thallus of the lichen. The thallus varies 
considerably in the different genera and species, according to 
the bark substratum on or within which they subsist. Heredity 
is manifested mainly in the character of the lirellae. 
CYTOLOGY. 
There is little to add to our knowledge of cytology. Moreau 
(1921) in his examination of Stictaceae found that the asco- 
gonium was a complex of uninucleate cells. Trichogynes were 
formed and reached the surface of the thallus, but degenerated 
without any copulation with spermatia. The ascogonium itself 
may become a plectenchyma; the asci and the paraphyses arise 
from the ascogonial cells. 
Bioret (1921) notes in his account of the asci and spores of 
Graphidaceae that the length of the spores is proportional to 
the length of the asci which in turn are proportioned by the 
depth of the apothecia. The spores in several genera are dis- 
tinguished by transverse septation into a varying number of 
cells; in those of the type of Graphis dendritica there are six or 
seven septa, division taking place first at the centre. After the 
first division, a second takes place in each cell close to the 
median septum, the inner cell does not divide again, but the 
process is repeated in the terminal cells. The outermost cell alone 
retaining the power of septation. He also notes that in Graphi- 
daceae as in many other lichens the fruit continues to form asci 
and spores for many years, though he does not find that 
sporulation is continuous. The cell division in polarilocular 
spores is discussed by Mameli (1920, 3). She found in Caloplaca 
aurvantiaca var. polycarpa many spores distinctly divided by a 
septum, and the septum was evident along with the channel of 
union between the polar cells; in other spores the channel 
tended to disappear. It is satisfactory to note the confirmation 
of septation in these spores. She also draws attention to the 
reaction of the apothecial tissues with potash: the tips of the 
paraphyses and in some cases the contents of the spore alone 
are stained crimson. 
PHYSIOLOGY. 
A study of nutritive salts in the lichen thallus was made by 
Salomon (1914) and of the exchange of substances between algae 
