
          Cambridge, 22 June 1851
Dear sir,
It was from no [?] in
interest that I looked so carefully at the lichens
you were kind enough to send me. But it has
been the result of my experience that I could best
satisfy myself in studying plants, when I gave myself
up to a particular group exclusively. This has got to
be my fixed habit now; and as I cannot devote the
whole time to Botany, I lay aside everything that
comes till enough accumulates for three or four weeks
works, and then go into it when the times comes
with all my strength. Still I glanced [added: or meant to] at every
specimen you sent, and had it not been at night,
should by no means have missed the Roccella, as
I did. You did not express your desire that I
should [crossed out: expre[ss]] give an opinion (immediately), upon
them, and so I laid them aside, to be worked up
when the time should arrive, with the other things in
the same predicament (including a box of goodly size
from Louisiana, and the last precious remittance
of Mr. Wright, kindly forwarded by you.)
The Roccell is a treasure. At p. 13 of my 
Synopsis I mentioned all that I knew relating to the
genus as possibily North American. But even with the
chance there indicated, I am sure I had very little
expectation fo its turning up on one Atlantick coast.
San Diego gives it to us, + thereby an interesting addit-
ional genus to your Flora. The specimens are branches
only + do not enable me to determine the habit - but
the flattened form  refers it to R. fuciformis. It does
not much resemble (in these specimens at least) the R.
fuciformis of the East Indies, or of Europe. It is perhaps
        