160 PROCEEDINGS OF THE AMERICAN ACADEMY 



group of islands, the different islands are apt to have each their own 

 peculiar species. In this instance, while the species on which this 

 characteristic genus was founded belongs to Hawaii, growing on the 

 high mountains of Mouna Loa and Mouna Kea, the second species 

 was found only on the island of Maui, at the base of a high crater ; 

 and a plant of an allied, but very distinct, genus was gathered on the 

 island of Kauai. The new Argyroxiphium has much larger capitula 

 than A. Sandwicense, from which it also strikingly differs in the total 

 absence of pappus, just as the Californian Lasthenia (Hologymne) 

 glabrata does from the genuine species of Lasthenia, Burrielia 

 (Baeria) chrysostoma from the other species of that genus, and Ptilo- 

 meris calva, Nutt., from its congeners ; adding another to a singular 

 class of cases, all occurring in the same part of the world. The 

 species may therefore be briefly characterized as follows : — 



"A. MACROCEPHALUM : capitulis nutantibus maximis (1^ unc. dia- 

 met.) ; ligulis discum vix sequantibus ; receptaculo conico; 

 pappo nisi coronula disciformis nullo. 



" The A. Sandwicense has a convex or depressed-conical, not a flat, 

 receptacle : the pappus is better represented by the figure of Hooker 

 {Icones Plantarum, tab. 75) than by the description of De CandoUe. 



"The allied genus referred to has much the habit of Argyro- 

 xiphium, but in its floral characters is more nearly related to Las- 

 thenia. As it is one of the most striking of the new plants obtained 

 during the cruise, it may be appropriately dedicated to the commander 

 of the expedition ; I have therefore characterized it, in the Botany 

 of the voyage, now in preparation, under the name of 



" WILKESIA, Nov. Gen. 



" Capitulum homogamum, multiflorum. Involucrum campanula- 

 tum, gamophyllum, subtri-quadrilobum, lobis apice 3-4-dentatis 

 villoso-ciliatis. Receptaculum convexum, nudum. Flores hermaphro- 

 ditaj, conformes. Corollse tubulosae, glabrae ; limbo dilatato campanu- 

 lato 5-lobo. Antherse ecaudatse. Styli rami cono hispidulo compla- 

 nato apice subulate superati. Achenia elongata, compresso-quadran- 

 gulata, ad angulos hirtella. Pappus persistens, e paleis 8-9 lanceo- 

 latis acuminatis rigidis hispido-ciliatis. — Herba grandis crassicaulis ; 

 foliis lineari-lanceolatis nervosis coriaceis, adultis glabratis tomentuloso- 

 ciliatis, caulinis subverticillatis basi coadunatis ; capitulis in paniculam 

 amplam digestis longe pedunculatis ; floribus ut videtur albidis, 



" W. Gymnoxiphium. — In Montibus Kauai, Ins. Sandwicensium." 



