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CHAPTER VIII. 
PRESERVATION OF FERNS FOR THE HERBARIUM. 
There is no group of plants better calculated for pre- 
serving in an herbarium than that of the ferns and fern- 
allies. These plants possess an active principle, consist- 
ing of a volatile oil and resin, which has destructive 
effects upon some of the radiate and annulose animals. 
Since the time of Dioscorides, the male-fern has been 
celebrated as a vermifuge. The species of Acarus and 
Anobium , so very destructive to the herbarium, are not 
far removed in essential characteristics from the entozoa 
which torment the human frame. No direct experi- 
ments have brought the principle to actual demon- 
stration, but it is a reasonable inference to draw, that 
those qualities in the ferns which are so obnoxious to 
the worms infesting the bodies of animals, brute and 
human, should be equally obnoxious to those relatives 
of the worms which infest dried plants. 
In preparing a collection of dried ferns, our first care 
must be to select perfect and typical fronds. There is 
too great a tendency in this, as in other and more im- 
portant matters, to affect the curious and the uncom- 
mon, and to neglect the true. When the whole of a 
fern-plant can be contained in a sheet of the herba- 
