MR. J. MIERS ON TWO GENERA OF PLANTS FROM CHILE. 143 
In Chorizema and Mucronea, the involucres are l-flowered, being 6-toothed in the 
former and bidentate in the latter; in Eriogonum and Chorizanthe, the inflorescence is 
generally terminal, and capitate in Mucronea, with three involucres, verticillately arranged 
in each flowering axil; but this plant, differing from all others, offers only a single stipi- 
tate involucre in each axil or dichotomy. From all these peculiarities, I naturally at first 
concluded it would constitute a new genus, which I proposed to call Zetraraphis, closely 
allied to the Oxytheca of Mr. Nuttall, described in the Journal of the Academy of Natural 
Sciences of Philadelphia (2nd Ser. i. 169). Although agreeing with that description in 
its similarity of habit, its linear radical leaves, a single few-flowered involucre in each 
axil, supported on a filiform pedicel, with its teeth armed with long rigid bristles, Oxytheca 
appeared to differ in its ramifications being trichotomous, in having only three sepals and 
three petals, and these all united in a tube nearly to the summit, in having six stamens, 
three styles and stigmata, in its achenium being compressed and 2-sided, and in its 
embryo being placed excentrically in fleshy albumen. These differences appeared suffi- 
ciently great to warrant the conclusion that the plant under consideration, though closely 
allied, was generically distinct from Oxytheca, and hence it was desirable to compare it 
with the Californian plant: this I had the good fortune to meet with in Sir W. Hooker's 
Herbarium, communicated by Mr. Nuttall himself, as an authenticated specimen of his 
Oxytheca dendroidea. I was greatly surprised, however, to find it so closely resembling 
my own plant in external appearance, and so like it in dimension, in the dichotomous mode 
of its growth, in the shape of its leaves, and in the size and aspect of its involucres and 
flowers, as scarcely to be distinguished from it. In my own specimen, the chief specific 
difference seemed to consist in the constant dichotomy of its ramifications, which are only 
divided into three branches at its first basal joint, in the bracts at the division of the stems 
not being quite divided to the base, its leaves not strongly revolute, the achenium not 
compressed, 2-sided and lenticular, and its flowers, with rare exceptions, being 4-merous, 
having their floral envelopes nearly divided to the base. Mr. Nuttall, in his generic cha- 
racter, states that the flowers are either dicecious or moncecious, that in the female flowers 
the perianth is closed to the summit and 6-toothed, that in the male and hermaphrodite 
flowers it is shortly 6-cleft, and he hesitatingly gives the number of stamens to be six; it 
must be remembered, however, that his examination was from dried specimens of plants 
collected by Dr. Gamble in the Rocky Mountains. As Mr. Nuttall includes in his genus 
Oxytheca, another section under the name of Gomphotheca, founded upon a very distinct 
plant, with dioecious pentamerous flowers, possessing a very different habit; as he nowhere 
states that the two other more legitimate species have moneecious flowers; as I have 
not noticed the flowers of the plant from the Chilean Andes to be otherwise than perfectly 
hermaphrodite; and as the floral characters of the Californian plants appear doubtfully 
stated, or made to include two distinct groups, and at variance in many particulars with 
the features I have observed,—I feel induced to remodel the generic features of Oxytheca 
in the following manner, in accordance with the facts I have carefully noticed in my own 
plant, modified in some degree by the circumstances stated by Mr. Nuttall. 
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