MR. J. MIERS ON TWO GENERA OF PLANTS FROM CHILE. 143 



In Chorizema and Mucronea, the involucres are 1 -flowered, being 6-toothed in the 

 former and hidentate 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 Tetraraphis, 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 dioecious or monoecious, 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 monoecious 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. 



