the Dillenian Herbarium. 115 
idea which most forcibly occurred to my mind was that of their 
necessarily imperfect nature ; but, on reading over what I have 
written, I am far more struck with the apparent presumption of 
undertaking thus freely to comment upon the works of the most 
celebrated naturalists that ever lived. I trust, however, the So- 
ciety will agree with me, that this presumption exists only in ap- 
pearance ; for I have done nothing more than observed what, had 
they enjoyed a similar advantage, they would themselves have 
observed long since, and the difficulty* of conveying an adequate 
idea of a plant by descriptions, or sometimes even by figures, is too 
great for it to be possible for the most accurate observer always 
to avoid mistakes in references. I have indeed one satisfaction, 
which is the consciousness that I incur no risk of a charge of de- 
traction ; for Dr. Roth, the author whose works have most fre- 
quently fallen under my notice, ranks too highly as a botanist, and 
has too many claims upon my esteem as an individual, to leave 
any apprehension of such a suspicion. I will only add that, spite 
of the progress made in our knowledge of the class Cryptogamia 
since the days of Dillenius, the excellence of his Historia Musco- 
rum is so great, and its utility to every student so indispensable, 
that, as the work itself is become extremely scarce, although im- 
pressions of the plates may far more easily be procured, 1 do not 
think any botanist, who has sufficient leisure for the undertaking, 
could engage in a more necessary task than the re-publication of 
the letter-press, adding specific names and descriptions from the 
writings of Linnaeus, Roth, Hedwig, and Acharius. 
Yarmouth, 
6th April, 1803. 
* This difficulty is far greater among the Conferva than among the Musci, or any other 
part of the Algae, unless high magnifying powers are employed : for want of these, and 
of colouring to his plates, they are in many instances absolutely useless. 
q 2 XI. Description 
