238 Rhodora [OCTOBER 
density that it will be most effective and yet not deposit a perceptible 
coating of the sublimate upon the plant and thus alter the appear- 
ance of the surface, so that it loses to a certain extent its natural 
condition, so important in the identification of plants. In extreme 
cases it has been found that such a coating of sublimate may render it 
difficult to tell whether or not a given stem was glaucous in nature, or 
to determine with a hand lens the precise amount and character of 
minute pubescence. If, on the other hand, the density of the solu- 
tion is allowed to sink much below saturation, a question arises 
whether the treatment is really effective. Many plants even in the 
dried state retain enough of their waxy super-cuticular coating to make 
it doubtful how thoroughly their tissues are reached by the solution 
during the brief wetting usually practiced. In this regard, however, 
it is to be admitted that an alcoholic solution would certainly be much 
more penetrating than an aqueous one. 
There is an additional difficulty in this mode of poisoning from the 
fact that many dried plants, such as Potamogetons, aquatic 
Ranunculi, and others of delicate texture, quickly curl or become 
hopelessly tangled during an attempt to dip them into a solution of 
any kind. Other plants have a chlorophyll so delicate and tissues 
so easily penetrated by an alcoholic solution that they emerge from 
even a very short bath in a spotted and disfigured condition, the 
alcohol having partially exercised its well known solvent action upon 
the green coloring matter. 
To prevent the curling of the specimens while they are drying 
after their bath, it is necessary, as already stated, to put them between 
driers, and thése blotters draw off the greater part of the solution 
which the plants have taken up. Herein lies one of the chief reasons 
why the treatment is not more efficient, for it is probable that such 
parts of waxy-coated stems and leaves, as come into direct contact 
with the blotters, lose practically all the solution which may have 
adhered to them, Such exposed parts must become, especially after 
further cleansing, as for example through the friction of a towel 
during the process of mounting and the ordinary rubbing of superim- 
posed sheets in the herbarium, vulnerable points for the attacks of 
the herbarium beetle. To overcome this difficulty, in some of the 
foreign herbaria, some more viscid substances and a small quantity 
of carbolic acid are added to the alcoholic solution of corrosive sub- 
limate, rendering it more adhesive. However, this sort of perma- 
