274 THE ESSEX NATURALIST.
the check given to work of this nature during the period of
the War, the number of papers published was considerably below
the normal.
The advance of botanical knowledge along ecological lines
makes it more and more evident that greater attention than
has hitherto been given should be paid to the Cryptogamic flora
of districts that are suitable for thorough botanical survey.
A means by which the Club can foster progress is that of
providing a well-arranged and fairly complete herbarium of
cryptogams, by the aid of which botanical members can obtain
a fuller knowledge of these plants, and a greater facility for
naming specimens gathered in the field.
The direction along which Lichenology has progressed during
the past ten years can be ascertained with some degree of accur-
acy from a summary, arranged under suitable headings, of
papers that have contributed to our knowledge of lichens during
the period 1911-1920. Such a record (appended to this paper)
makes it quite possible to follow the trend of recent research
by British lichenologists.
In addition to papers dealing directly with lichens, articles
covering a wider range, but at the same time contributing new
matter concerning these organisms, are included in the list.
Papers may be conveniently grouped according to their
subject matter under the four heads1: Records, Ecology,
Morphology and Physiology, Symbiosis. The percentages of
the numbers placed under each heading are approximately:—
Records 45%, Ecology 39%, Morphology 3%, Symbiosis 13%.
In compiling such a bibliographical summary it has been
found necessary occasionally to include a paper under two dis-
tinct headings, viz., when it consists for the most part of lists
of recorded species, and at the same time includes, interspersed
between the lists, important ecological notes.
It is not suggested that this summary approaches the point
of exhaustion, but at the same time it is not probable that later
additions to it, of papers that may be inadvertently omitted on
this occasion, will materially modify the results already obtained.
Papers under the heading "Records," are not referred
to further than to say that they include lists of lichens,
1. The numbers in brackets refer to the serial number of the article in the appended Biblio-
graphy.