Fes. 1905. ] BOTANICAL SOCIETY OF EDINBURGH. 77 
Each specialised herbarium should have an underlying 
aim or idea which it is designed to illustrate, and to which 
other considerations should be subordinate. Thus they can 
readily be combined into larger collections to any extent, 
and both usefully and advantageously. But their value lies 
in the merit of the conception that guides the formation of 
each, and in the care exercised in giving material form to 
the guiding idea. Thus, if it is desired to illustrate the 
principles of classification, a large collection of plants, merely 
dried and mounted, will be far less useful than fifty or 
a hundred species carefully selected for the purpose, 
illustrated with preparations of the various parts in so far 
as they can be shown in the dried state, supplemented by 
drawing of obscure features, and by descriptions or notes 
calling attention to the characters distinctive of the grades 
in classification, and of those that are merely based on 
resemblances and do not indicate kinship of species. For 
the purposes of such herbaria, common plants, as affording 
abundant material from which to select the most suitable, are 
to be preferred to rare species, in all but the few cases where 
the latter supply Luks that have ceased to exist elsewhere. 
Let us now turn for a little to the type of herbarium 
that more nearly corresponds to the generally accepted 
meaning of the word, and clearly that intended by the 
committee of the British Association in its estimate of the 
chief value of a herbarium. It consists of a more or less 
extensive collection of dried plants, the work of its owner 
(to whom if may possess a very special value as recalling 
pleasant holidays or well-spent efforts), or built up by the 
labours of many workers, and brought together from many 
lands. The value to botanical research of the great national 
herbaria, and of many private ones, is recognised by every 
botanist. The loss to science would be very great were any 
one of these great herbaria destroyed; and their preservation 
is looked on as a public duty. They have been indispensable 
in the advance of botanical research, and contain materials 
for long-continued investigations into geographical distribu- 
tion and systematic botany. But their very extent and 
resources make it impossible for individual botanists to hope 
to rival the great herbaria in these fields, or to pursue these 
studies at a distance from such collections. A_ botanist 
