I am most clearly of the opinion that any person who will make extensive collections of North American plants, both Northern and Southern, and include also a good collection from Santa Fé, the Platte country, etc., have his sets named according to our work, and who would devote four or five years to the business, could, if he were really industrious and prudent, realize $1000 per annum (clear). He should continue my grass-book for one thing, giving loose sets only for the present price, and while from time to time he sells off collections as he can, should retain some fifty sets in all the most interesting genera or small families, get all the species, and publish them in monographic sets. Knieskern could make, with the aid we would gladly furnish, at least ten times as much money, as long as he lives, as he ever will at physic, besides being engaged in a much pleasanter way. I know how all this should be managed now. Now for Dr. Clapp. Tell him that Brown informs me that he does not think jewel lenses can be depended upon as possessing any advantage over glass. He has an excellent sapphire one, but that is a mere chance, and no other has been made anything like it. They are now almost never made, and appear to be going wholly out of use. His other matters I will take in hand, but he must not expect $20 to procure a doublet 1/40th inch focus, two micrometer glasses, and a case of dissecting instruments. I have some engagements before me with microscopical people, and when I get from them all the information I can, I will set about these affairs more understandingly.... Saturday evening, February 9.--I have been engaged nearly the whole day upon the herbarium you so much wished to examine, viz., that of Walter. I have not yet finished it, and find the examination very tedious, as the specimens are very often not labeled, except with the genus in his “Flora,” so that I have first to make out his own species, and then what they are of succeeding authors.