Notice of a Flora of North America. 279 



posiicB, which is justly termed by De CaiidoUe, " Ordo omnium 

 naturaHssimus et vastissimiis et ideo difficilhmus," and which, 

 Drs. Torrey and Gray, following in that respect the arrangement 

 of Lessing, divide into three sub-orders, comprising, together, 

 eight tribes, which are of very unequal importance in respect to 

 the number of genera which they embrace. The first tribe, 

 VernoniacecB, is very small, being limited to six genera, of which 

 Vernonia is the most important ; and we notice a new species 

 from Florida. The second tribe, EupatoriacecB, comprises twen- 

 ty-one genera, none of much importance, (within the geograph- 

 ical limits of this work,) except Liatris and Eupatorium. Of 

 the former genus, a new species is introduced from Georgia, and 

 three species, as heretofore characterized by botanists, are now 

 removed to the genus Carphephorus, established by Cassini on 

 the Liatris squamosa^ Nutt., our authors observing, that "on ex- 

 amining the allied species of Liatris^ we find that all those with 

 many-flowered heads disposed in corymbose cymes also belong 

 to the genus, which is well marked in habit." In this tribe, we 

 have also a new species of Coslestina, from Key West and Flor- 

 ida, and a well known tropical species of Ageratum is recorded, 

 for the first time, as a native of the United States. The authors 

 remark, that these two genera are not sufficiently distinct. We 

 further notice, in this tribe, a new species of Clavigera, DC, 

 from the interior of Texas. We now come to the important 

 tribe AsteroidecB, of which the first subdivision (Eiiasterecp.) oc- 

 cupies nearly one half of the present number. This section is 

 confined to the several genera, and sub-genera, comprehended 

 under the popular name of Asters, which have so long been the 

 terror and stumbling-block of American botanists. It appears, 

 from an introductory note, appended to the genus Astei; that Drs. 

 Torrey and Gray have enjoyed great advantages in the study of 

 this most difficult tribe, being " greatly indebted to several bota- 

 nists and public institutions in this country, for the use of their 

 entire collections of American Asters ; and we would especially 

 render our acknowledgments to Sir Wm. Hooker, who, by most 

 liberally entrusting to our care his vast materials in this and other 

 allied genera, has afforded the most important assistance." * * * 

 The original genus Aster, of Tournefort and Linnasus, has been 

 largely subdivided by modern botanists, and, according to their 

 arrangement, is made to consist of some eight or ten genera. 



