Many other botanical workers wrote on this genus during the period covered and some of them did very valuable work in describing the various species but their work has not been referred to because it did not add to the knowledge of the genus as a whole. The first man to write a monograph on American grapes was Rafinesque,[119] who published in 1830 a paper bound volume entitled _American Manual of the Grape Vine_, etc. Rafinesque, who was long a resident of the United States, had an opportunity to acquire knowledge on the subject upon which he wrote second to none other. His description of the genus is similar to that of his predecessors and very good; but here all similarity ends and practically all value. After having made forty-one species, the greater portion of which have names given by himself, he says: "By the above enumeration of our Grapes I have done for this genus what Michaux did for our Oaks. Owing to the great confusion of former authors, and the difficulty of comparing the leaves and fruits of all the species, it is hardly as perfect as I should wish. Rigid botanists may perhaps wish to reduce this species to a minor number or consider some as hybrids: if they can find good permanent collective characters, let them reduce our Grapes and Oaks to a dozen species. But the angular or striated branches, the long or short petioles, the oval, cordate or reniform leaves, etc., must always be deemed essential specific characters, and several of my new species, such as V. bracteata, V. angulata, V. peltata, V. canina, V. blanda, V. longifolia, V. acerifolia, V. amara, V. prolifera, etc., must be deemed very distinct." None of those of which he says "must be deemed essential specific characters" is now so considered and the species which must be "deemed very distinct" are many of them unrecognized and none of them known by the name which he gave. Le Conte, about the middle of the last century, did much work in the botany of grapes, publishing several papers in the _Proceedings of the Academy of Natural Sciences of Philadelphia_. These were in the nature of monographs although they were not, so far as known, published separately. He gives twelve species generally taken from other authors.