
          Washington City March 10th 1850.

Respected Sir.

I crave a thousand pardons for not having acknowledged
before this time, the receipt of your favour of Jany [January] 16th, 
as also a copy of Swartz Sy. Fil. [Synopsis filicum] received through Mr. Drayton; 
the delay was occasioned by my having to wait from day to day, for 
proofs of the Fern plates, which I intended to send with the descriptive part 
of the work, determining to write [crossed out: ?] to you at the same time; these 
proofs I received a week ago today (not complete) and without delay 
set about numbering and lettering those that corresponded with the mss. [manuscrip] I 
had then prepared, which amounted to 290 pages; this, and all the 
proofs (save three) of species figured belonging to mss. [manuscript] sent, I have delivered over 
to Captn [Captain] Wilkes, to be forwarded to you through Mr. Drayton. And it may not 
be altogether agreeable [crossed out: ?], that [crossed out: the] [added: my] great obligation [crossed out: ?] [added: to you], has to be 
arrived at through this peculiar channel; but I could not well avoid it, being 
anxious that both Captn [Captain] Wilkes and Libry [Library] Committee should be aware of the amount 
of labour on my work which would fall upon you to perform; and it is more 
than I at first calculated on myself. I do not know that much improvement 
has been wrought by me on the copy of mss. [manuscript] sent, from that which we partly overhauled
in Novr [November] last, but at all events, in the few hours which was from time to time 
spent on it, I endeavoured to make many of the remarks more intelligible, and 
through the whole work, have transposed transposed some of the heads, at your suggestion. 
Too small a space was left to insert the references to the plates, as you will perceive that
they are much crowded, and perhaps not altogether correct as to expression. In 
the references to authorities, I may have inserted English, where it ought to [crossed out: ?] be Latin 
as and for et, and Author for Auct. My essential characters may appear 
sometimes long, but they are not more so, than some of Sir Wm J. [William Jackson] Hookers. 
I would remark, that the plates of some of the proofs sent, I am going to have 
altered, by inserting scales and having on certain parts where they have
        