AND GENERA OF PLANTS. 371 
Subtribe [V.—TacerTinez. 
*RIDDELLIA. 
- Capitulum many-flowered, heterogamous; rays feminine, three to five, coria- 
ceous, persistent, dilated, equally and obtusely three-lobed, six-nerved; discal 
florets hermaphrodite, tubular, five-toothed, the dentures glandular. Stig- 
mas subcapitate, obtuse, minutely pubescent. Involucrum cylindric, com- 
posed of eight ingrafted leaflets. Achenium slender and conic, prismatic, 
smooth. Pappus paleaceous, five or six-leaved, segments lanceolate, acumi- 
nate, nerveless, similar in the ray. Receptacle naked, minute.—A slenderly 
branching, aromatic herb, with alternate, oblong-linear, subtomentose leaves ; 
branchlets corymbose, three to five-flowered; persistent rays apparently yel- 
low, (reddish-orange after inflorescence;) involucrum densely sericeous with 
long hairs.—(Named in respect of Professor Riddell, a botanist, who. has 
explored the interior of Texas.) 
Riddellia * Tagetine. 
Has. The southern range of the Rocky Mountains, towards the sources of the Platte. A very 
elegant plant, with the habit of a Zinnia, but having the involucrum formed of a single series of 
united sepals. The rays are very remarkable, appearing as rigid as bere, and remain per- 
pe flat after inflorescence, as in Zinnia. 
*SOLENOTHECA. 
Capitulum few-flowered, heterogamous; rays feminine, very few and small, 
(two or three.) Involucrum an entire, even, cylindric tube, with a short, 
- five-toothed border. Receptacle naked. Achenium fusiform, compressed, 
somewhat four-sided, partly stipitated at the base, pubescent. Pappus pa- 
leaceous, palee elongated, setiform, of equal length, but unequal thickness, 
ciliated, and almost plumose on the margin.—A small annual of Peru, with 
: slender, spreading branches; leaves opposite and alternate, pinnatifid. Flow- 
ers terminal, fastigiate; liguli few and very small. Nearly allied to Tagetes, 
but with a very different pappus, and a peculiar habit—( Named from oaAmp, 
a tube, and Oxxn, a sheath, in allusion to the cylindric calyx. ) 
