OF ARTS AND SCIENCES. 97 



ASTER. The revision of this vast genus is not yet completed, 

 owing to the great difficulty which is experienced in settling the sy- 

 nonymy and the limits of some of the earlier as well as of the later 

 known species. It is intended to accept the genus in the wide extent 

 assigned to it in the Genera Plantarum of Bentham and Hooker, 

 at least so far as North America is concerned, and also to include 

 Brachyactis. The subgenera may be arranged in two series ; the first 

 of perennials, the second of annuals and biennials ; and an endeavor 

 has been made to dispose of the perennial Asters under the following 

 subgenera. 



§ 1. Ajiellastrum, best marked by its broad and obovate very flat 

 achenia with callous-nerved or thickened margins, and no lateral nerves. 

 Here A. alpinus and the yaviety Jlaccidics, and the wholly Old World 

 A. Amellus, L. 



§ 2. Megalastrum. This was indicated in PL Wright, ii. 75, 

 and it connects the genus with Townsendia. The head, as the name 

 denotes, is very large, and the leading character is found in the 

 unusually coarse and rigid bristles of the pappus. The species are 

 A. tortifolius, Gray (Aplopappus tortifolius, Torr. & Gray), and A. 

 Wrightii, Gray {Townsendia § Megala&trum Wrightii, Gray in Bot. 

 Mex. Bovmd. 78), Texano-Arizonian species, more or less suflfrutescent. 



§ 3. Heleastrum. DeCandolle's genus of that name, well restored 

 as a section by Bentham, which also has unusually coarse and rigid 

 pappus-bristles, the stronger ones somewhat clavellate at tip ; the 

 coriaceous-foliaceous bracts of the involucre are somewhat equal in 

 length ; the achenia narrow, mostly slender, little compressed, and 8-10- 

 nerved. A. eryngiifolius, Torr. & Gray, and A. spinidosus, Chap- 

 man, are referred here, along with the original A. paludosus. Ait. All 

 three are low pine-barren species of the Southern Atlantic States. 



§ 4. Hesperastrum was indicated in the Botany of California, 

 under § Machoeranthera. The single species, A. Shastensis, of Mt. 

 Shasta, California, is truly perennial, has narrow and hardly at all 

 compressed achenia traversed by 5 strong nerves and intermediate 

 striae ; but the pappus is soft. The leading peculiarity is in the neutral 

 rays, after the manner of Gorethi'ogyne, of which it has somewhat the 

 habit. But the style-appendages are slender and naked. 



§ 5. BiOTiA, a well known group, with appendages to the involu- 

 cral bracts so short or obscure that the section might be placed next 

 to the sections Dcellingeria and Orthomeris, while on the other hand 

 it is neax-ly related to Sericocarpus., also to the Calliastrum group 

 of the 



VOL. XVI. (n. 8. VIII.) 7 



