The letters are not overly scientific but with enough details that the structure of a plant or flower can be discerned if you have a specimen with you. The letters are very readable. Here he is reproving them for sending him flowers without the leaves

“Here, dear cousin you have the names of those plants which you sent me last. I have put a mark of interrogation to those which I had any doubts of because you had not taken care to put the leaves with the flower, and they are often necessary to determine the species, especially to so slender a botanist as I am. When you arrive at Fourriere you will find most of the fruit trees in flower; and I remember you requested some directions from me upon this article. At present I can only give you some hints upon the subject, because I am very busy, and yet I would not have you lose the season for this examination.
You must not my dear friend, give more importance to Botany than it really has; it is a study of pure curiosity, and has no other real use than that, which a thinking sensible being may deduce from the observation of nature and the wonders of the universe.

Well that tells me who undertook a degree in Botany!

The whole book is available online