240 Rhodora [OCTOBER 
use of arsenic was then promptly given up and happily the 
physiological effects soon disappeared. 
Thoroughly discouraged by the ineffectiveness and danger of the 
poisons hitherto employed, Dr. Sereno Watson, then in charge of 
the Herbarium, decided to give up the poisoning entirely, and to trust 
on the one hand to the tightness of the cases and on the other to the 
vigilance of the staff to protect the collection from insect depredations. 
After three or four years, however, it was found that both the small 
brown “herbarium beetle " (.S/odrepa panicea) and a more minute and 
colorless member of the Psocidae, the * book-louse” (Atropos divina- 
toria)! were increasing at an alarming rate and becoming pretty gener- 
ally distributed in the collection. ‘This was doubtless due in part to 
the fact that some large herbaria, acquired about that time, notably 
the collection of the late Dr. George Thurber, were badly infested by 
insects. In the injury to specimens at this period, it was clear that 
the recently inserted specimens, which had not received the corrosive 
sublimate or arsenic treatment, suffered most. ‘This, however, can- 
not be taken as an unqualified proof of the value of these poisons, 
for many specimens of older date, known to have been so treated 
were found to be infested and injured by the insects, and the fact 
should be borne in mind that the first five years after the preparation 
of an herbarium specimen, before it reaches the final stage of com- 
plete desiccation, is the period when it is most liable to damage by 
insects. 
The tightness of the cases, with the insects already inside, was 
naturally found to have only a negative value. Some more drastic 
means had to be found, and accordingly a tin can was devised for the 
fumigation of the sheets with carbon bisulphide. It was modelled 
upon a type of case successfully used by Mr. William Brewster in his 
valuable collection of birds, but was provided with eight shelves for 
herbarium sheets, of which it would hold about a thousand. ‘The 
front of the case, which was also of tin, was provided on the edge 
with a metal phlange turning inward, which fitted into a metal groove 
in the case. This groove was lined with a convex strip of soft rub- 
ber, which being compressed by the phlange of the cover, when the 
latter was fastened on by ten external clasps, formed an essentially 
air-tight fitting. At the bottom of the can, under the lowest shelves, 
two spaces about two inches high were left for the insertion of shal- 
! For the identification of these insects I am indebted to Mr. Samuel Henshaw. 
