200 Transactions British Mycological Society. 
Bachmann (1922) has published a paper on the physiological 
aspects of the lichen thallus immersed in limestone. He con- 
siders that water supply is the chief advantage gained by the 
plant. He tested the rate of absorption for limestone con- 
taining—or free from—lichens, and he found that limestone 
harbouring lichens had a greater capacity of absorption and re- 
tained the moisture longer than the lichen-free rock. 
Comparing lime lichens with each other he found that those 
associated with Pleurococcus gonidia showed less capacity of 
water absorption than those with Tventepohlia. In the latter 
case the stone is more deeply pierced by the wandering filaments 
of the alga. He contrasted silicicolous lichens with calcicolous 
and found that the latter had the greater capacity of absorption. 
Considerable use is made of reagents by systematic workers, 
notably by Zanfrognini (1917) in his work on Somali lichens. 
Bachmann (1922) found methyl-green in acetic acid of value as 
a colour reagent: it stained the hyphae of fungi parasitic on 
lichens, while the lichen hyphae themselves were unaffected. 
It would be interesting to see the test applied to the group of 
half-lichens that are mid-way between lichens and fungal 
parasites. 
During the war, there arose in all countries the necessity to 
utilize every kind of food supply. Hesse (1915), well known for 
his researches on the chemistry of lichens, turned his attention 
to their economic properties. He worked out a comparison of 
their sugar content with that of potatoes and found that for 
Cetraria islandica the proportion was I : 3°35; for Cladonia 
vangiferina, the reindeer-moss, I : 2:5. Both of these lichens 
therefore might be used with advantage as food for man, if the 
acid products were eliminated. Jacobj (1916) in a pamphlet 
also encouraged the use of lichens as food stuffs. He mixed 
reindeer-moss with the food of young pigs with the result that 
the animals throve better than with ordinary food alone. Rabbits 
and hares were fed with Evernia prunastn after extraction of the 
acids and the results were also satisfactory. 
Bernt Lynge (1921) draws attention to the value of Cetraria 
islandica as a food supply and to Cladonia alpestris as a fodder 
plant; as such the latter is largely employed by farmers in 
countries bordering on arctic regions. 
BIONOMICS. 
Under bionomics we touch on many sides of lichen develop- 
ment. Santha (1916) tested sections of lichens of the genus 
Physcia with polarized light. In most species the upper cortex 
was clear, the other tissues were more variable as regards the 
transmission of light and in one group which he designates 
