AUSTRAL-AMERICAN REGIONS. 



75 



carpus, one of the most frequent and characteristic plants. — A variety 

 of slender-leaved Plantagos. — Two or three Malvacece, having much of 

 the aspect of Potentillas. — A Poriulaca, conspicuous at a long distance 

 from the brilliancy of its large reddish-purple flowers. — Some very deli- 

 cate ornamental plants ; as a slender PuJijijala having the habit of our 

 Polygonellas ; and an Ox'a7/s with leaves cloven into two slender lobes, 

 like horns. — CactacecB, rare and singularly inconspicuous in the land- 

 scape, but presenting some remarkable species ; as an Opuniia having 

 its stem-joints ovoid or egg-shaped ; a species having cylindrical stem- 

 joints ; a Melocadiform Gereus, sometimes compound or agglomerated ; 

 and a MamiUaria? with flattened apex even with the surface of the 

 soil, so as, except where growing in companies, readily to elude obser- 

 vation. — But of all the vegetable productions, the most singular was 

 a Mtdinum, an Umbelliferous plant that although herbaceous, seemed 

 to emulate the spinescence of the shrubs; with leaves like trifid spines, 

 and resistant interlaced stems and branches, converted into a sort of 

 impenetrable green bunch. 



In the midst of the all-pervading structural modification, two spe- 

 cies of plants, an J-sc/epias and a Za?-re«, continued normal; maintain- 

 ing their large freshly-herbaceous leaves, as though insensible of any 

 prevailing drought. The Asclepias being, therefore, an exact counter- 

 part to the A. (Calotropis) gigantea of the Cape Verd Islands and 

 Oriental Desert ; the Larrea proving, at the same time, to belong to a 

 genuine Desert-tribe of plants, the Zygoplujllacece. 



The infiltrated ground. In striking contrast with the adjoining 

 upland, the marshy ground on either side of the river was thickly- 

 clothed and green with herbage : but the plants, belonging to Tribes 

 that occur in similar situations elsewhere, were comparatively uninte- 

 resting. Scirpus Jacustris? was here intermingled with reeds; as a 

 Deyeuxia, conspicuous from its large silver-white panicles, and a 

 Pliragmites. The intervening sj)aces being occupied by a more hum- 

 ble growth of Glumaceous or grassy plants ; as Scirpece, two species of 

 Carex, some saline grasses, as Uniola and Spartma, and two species of 

 Juncus; while here and there, and along the margin, other herbaceous 

 plants were met with, as a Sisyrindivum, a minute-flowered Lytliruin, 

 a iSamolus, Lwiosella, a TiUcea, two species of Hydrocotyle, an Apiuyn, 

 two species of Ery)iginm, and a Gratiola-like but ornamental Qerardla. 

 A dead tree, fifty feet by two feet in diameter at base, had floated 

 down the river, bringing entangled the living branch of a iviUoiv; 



