284 
THE ESSEX NATURALIST. 
with a growth of green autotrophic flagellates, now ready to 
take advantage of the penetrable tissues of the enfeebled hosts 
in their demand for a benthic substratum.” The green flagel¬ 
lates supply the place of the original green film of the surface 
layers, and thus the tissues of the denuded central axis are able 
to continue their metabolism at the expense of the waste carbo¬ 
hydrate and liberated oxygen that is available in the vicinity of 
the newly acquired green autotrophic cells. 
It is evident from what has already been said, that the greater 
number of papers on lichen ecology consists of those relating to 
the sea-coast. It is possible that this is so because such 
localities are more accessible than high mountain summits, which 
need to be visited frequently if effective work is to be accom¬ 
plished, for the greater part of the observation can only be 
carried out while the lichens are in situ. 
Contributions to our knowledge of the ecology of the lichens 
of lowland woods have not been forthcoming to any great extent. 
It would appear that an increasing number of botanists are 
being attracted to the subject of lichens ; but the scarcity of 
reliable guides, both for field work and for the laboratory, has 
militated against the pursuit of lichenology in this country. 
We can, however, now look forward, to meet this want, to the two 
volumes that are announced as in the press, both of them by 
Miss A. Lorrain Smith, one being a volume of the “ Cambridge 
Botanical Handbooks ” and the other a book for field work, 
somewhat similar in size and volume to “ Hayward’s Botanist’s 
Pocket Book.” It may here be noted that photo-micrography 
has been recently employed, for the first time in this country, 
for illustrating papers dealing with lichen symbiosis and 
lichen spores. 
I take this opportunity of thanking Professor F. W. Oliver 
for lending me lantern slides and specimens for exhibition, and 
Mr. J. H. Pledge for the very valuable help he has given me 
in making photo-micrographs, from my preparations. 
BIBLIOGRAPHICAL SUMMARY. 
The titles of papers are arranged in sections according to 
the chief feature of the contents, and also in chronological order, 
except when more than one paper by the same writer has to be 
