R. C. McLean. 
103 
THE UTILIZATION OF HERBARIUM MATERIAL. 
By R. C. McLean, 
Lecturer in Botany at University College , Reading. 
H OW many plants and families of plants remain imperfectly 
understood, for lack of adequate available material, can be 
known only to the professed systematist; but among such forms 
there are many with great promise of interest, and some at least, 
for instance the Balanopsidaceae, Anonaceae or the Lacistemacese, 
which may prove of considerable importance to the general scheme 
of the Angiosperm classification. 
In almost all such cases the only material upon which scientific 
investigation is or has been possible is dry herbarium material, 
often of considerable age or indifferent condition of preservation. 
Although it has long been customary to practise morphological 
analysis with such material, by simple soaking in water, either with 
or without heating, yet the results so obtained are seldom perfectly 
satisfactory, while the amount which can be learned of systematic 
affinity by macroscopic analysis of a flower, though valuable in 
itself, is confessedly incomplete, and has indeed failed, in many 
notable instances, as an index of affinity. There remain besides 
very many cases in which more or less dubiety exists, which a more 
intimate knowledge of the structures involved might well remove. 
These considerations have led me to seek a practical method 
for the restoration of dried vegetable tissues as nearly as possible 
to their original state, in order that the microtome might be used 
in their examination. 
There are several classic instances of the successful use of 
herbarium material in anatomical work. Among others, De Bary, 
Van Tieghem, Radlkofer and Solereder may be cited, while 
Tunmann (/) has illustrated how it may be employed for bio¬ 
chemical purposes, but apart from these fundamental works the 
method seems to have been neglected, especially since the elabora¬ 
tion of histological technique has produced more exacting require¬ 
ments in regard to the quality of the material, and the growth of 
comparative morphology has rendered serial sections indispensable. 
Even for such purposes, herbarium material may be used; there are 
few structures too delicate for resuscitation, apart from actual 
protoplasm, especially if the specimens have been thoroughly and 
rapidly dried in the first instance. In this connection it may 
perhaps be allowable to draw the attention of collectors more 
