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receive the return parcel; or, what comes to tlie same thing, he may 
send his contribution through a public herbarium. Many university 
and museum herbaria are sadly lacking in modern material of our 
changing flora, and their content of newly-described species is largely 
a matter of chance. To them the Exchange Section offers an oppor- 
tunity to expand and keep up-to-date. It is noteworthy that three or 
four public herbaria are regular contributors now, and others are in- 
vited to consider whethei’ they could not mutually benefit through the 
Exchange. 
What can the collector who wants authentic material but is not him- 
self an expert, offer in return? For many years now, interest in and 
knowledge of critical groups on the part of amateur botanists, and 
especially those in the provinces, has been waning. This was not sur- 
prising, for information on these groups was scattered through an 
ever-growing volume of original literature, often difficult to correlate 
and only available in a few big libraries. The publication of Clapham, 
Tutin and Warburg’s new Flora of the. British Isles has changed all 
this, and puts into everybody’s hands the means to identify plants which 
foi- too long have been the purview of a few experts. A specialist’s time 
is often preoccupied, and he relies to an extent not always realised upon 
the amateur to supply material from areas where he has no opportunity 
to explore himself. Interesting aliens and hybrids, too, are acceptable 
material, and turn up at unexpected times and places. Hybrids should 
if possible be accompanied by specimens of the putative parents. The 
Flora will also suggest many other items which are unknown to or mis- 
understood by the majority of botanists. However, indiscriminate sub- 
mi.ssion of the commonest species of a genus, merely because that genus 
happens to be critical, is not helpful. An apparently common plant may 
be of particular interest in a particular spot (e.g., for peculiarities of 
habitat or distribution), but if so it should be accompanied by a note 
giving details. 
Material from abroad is also eligible, if it has a definite bearing upon 
the study of the British flora. Foreign examples of critical British 
forms, related plants, and authentic examples of plants doubtfully re- 
ported as British, are especially welcome. The opportunity is thus 
open for herbaria abroad to acquire British specimens by exchange. 
To sum up, acceptable material may be classified as : critical species 
or subspecies, (a) from experts, illustrating new, little-known, or mis- 
understood forms, (b) from general collectors, illustrating distribution 
and providing material for discussion and reference; unusual varieties; 
geographical and ecological variants; other material illustrating cur- 
rent taxonomic or phytogeographical work ; new, unusual, or little- 
known aliens ; foreign material for comparison with British. About 
10-15 sheets is at the moment the most suitable number per gathering. 
To turn now to affairs of the present season, as already said there 
has been a great improvement both in quantity and quality this year, 
but the number of individuals contributing is still too small. One note 
of tragedy has been the passing of Mr. F. Rilstone shortly after he had 
