ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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Frequently they take origin after some injury to the thallus, or they are 
induced by the urgent growth of the algae. Isidia are of service as 
subsidiary reproductive bodies. Portions of the thallus are of service 
in regeneration if the medullary tissues are present ; the cortex, possibly 
owing to the felted hairs on the surface, takes no part in the renewal of 
growth. The influence of light, which is a necessity for the life of the 
gonidia, is one of the essential factors of thallus regeneration. Moisture, 
which is also of influence, depends on the connexion of the regenerating 
thallus with the water storage of the substratum. Regeneration did not 
follow under a moist bell-glass if the substratum was a mica plate 
instead of the normal earth or moist clay. A. L. S. 
Lichens of Haslemere District. — H. H. Knight {Trans. Brit. 
Mycol. Soc ., 1922, 7, 225). Most of the lichens found at the Spring 
Foray, Haslemere, were growing on wood ; the few saxicolous species 
collected occurred on stone walls, etc. The list numbers about sixty-six 
species. A. L. S. 
Determination of Lichens in the Field. — W. Watson ( Journ . 
Bot., 1922, 60. Suppl. 17-28). The author has given a further instal- 
ment of his key for lichens from field characters. Mostly he deals with 
genera only, but not infrequently species also are included. He has 
given an additional key to those with crustaceous thallus when the 
fructification is wanting. A. L. S. 
Physiology of Crustaceous. Lichens. — E. Bachmann ( Zeitsch . 
fur Botanik., 1922, 14, 193-233). The author comments on Zukel’s 
view that the immersion of the thallus in limestone was a shelter 
against the depredations of animals ; he considers, however, that water 
supply is the chief advantage to be gained. The research was carried 
out on herbarium material which was exposed to dew or rain or soaked 
in water after being thoroughly dried. The wet thallus was then 
exposed to sunlight. In nature water is absorbed from rain, dew or 
moist air. The rate of water absorption from these different sources 
is calculated for a number of lichens, and the evaporation of water from 
the specimens is also calculated and compared. Comparison is further 
made with samples of limestone free from lichens. The stone contain- 
ing the lichen thallus has a greater capacity of absorption than the free 
stone, and also it retains the moisture longer. In comparing lime 
lichens with each other he finds that those associated with Trentepohlia 
have a greater capacity of water absorption than those with Pleurococcus 
gonidia — in the former the lime is more deeply pierced by the pene- 
trating filaments of the alga. He contrasted silicicolous lichens with 
calcareous, and found that the latter had again the greater capacity of 
absorption. A. L. S. 
Cultures of Nostoc-gonidia from Peltigera Species. — K. Linkola 
{Ann. Soc. Zool. Bot. Fenn. Vcmamo, 1920, 1, 1-23, 1 pi., 7 figs.). 
The author cultivated the gonidia of eight species in various culture 
media. The algae not only grew' well but formed hormogonia, the first 
time these bodies have been cultivated from the lichen ; occasionally 
they developed into'spores, at other times they formed Nostoc colonies. 
