terials they have to work upon. Thus, the Solanaceaæ, carefully described by an apparently judicious appreciator of species, might have been doubled in number in the hands of the monographists of the order in the Prodromus. The Myrtaceæ, elaborated with all the industry, and zeal, and perhaps haste of a young botanist, might have been reduced by one-fourth by the close scrutiny of botanists more accustomed to appreciate the variations of species or of individuals. The principles upon which genera are made or adopted are also as different in different monographs as the estimation of species. In one portion of the Flora large natural genera are left intact, and endeavours have been made to group the smaller ones established on individual or uncertain characters; whilst in other parts (e. g. Acanthaceæ or Cyperaceæ) the great object seems to have been to multiply long-winded, harsh-sounding generic names, with or without characters.
As to the materials at the disposal of the various monographists, as no part of the Flora is worked up in the country itself, they can only consist of dried specimens, preserved in herbaria, with the memoranda accompanying them, and are chiefly made up of collections made in Brazil by German, French, or English travellers. Among the most im- portant of them, the original and most complete sets are deposited in different capitals of Europe. Those, for instance, of Langsdorff and Riedel, are at St. Petersburgh; of Sellow, at Berlin; of Pohl, Schott, and Mikan, at Vienna; of Martins and Prince Neuwied, at Munich; of Blanchet, Salzmann, and Vauthier, at Geneva; of A. de St. Hilaire, Claussen, Gaudichaud, Guillemin, and Weddell, at Paris; of Gardner and Spruce, at Kew, &c. The large herbaria in each of these towns contain also, it is true, more or less perfect sets of duplicates from all the others, as well as of the less general collections of Pœppig, Luschnaht, Lhotzky, Regnell, and others; and for the purposes of this Flora, specimens have been lent from several herbaria; yet it is only in the towns above mentioned that access can be had, respectively, to the explanatory memoranda accompanying the original sets. Very few, therefore, of the contributors have been in circumstances which allowed them the full use of all, or even of the greater number, of these complete collections. Most have worked upon one or two complete ones, with duplicates from others. Dr. von Martius has sent the Munich specimens at his disposal, with his valuable memoranda, to, we believe, all his collaborators. The Russian materials have been very liberally lent to several who had applied for them; the Sellowian and Pohlian materials have been available to most of the German contributors; everything that Geneva could supply has been lent to those who were at the same time working up corresponding monographs for the Prodromus. Paris and Kew have at different times lent largely for this and other works; but these herbaria have now acquired so much importance and value, that it has been found necessary, in both establishments, to make it a rule no longer to suffer unique or authenticated specimens to be removed, even for a short time; and visits to Paris and Kew are now almost indispensable to the systematic botanist who would make his monograph at all complete. The great di-
