198 PROCEEDINGS OP THE AMERICAN ACADEMY 



nentibus cum 2 intermediis parvis vel minimis; staminibus 6, filamentis 

 brevissimis. — " Reservoir Hill," Placerville, California, Mr. Rattan. 

 An insignificant weedy plant, three or four inches high, the branches 

 when old fragile at the joints, as in many other species, in habit resem- 

 bling O. procumbens. Fruiting involucre with its broadly obpyramidal 

 tube a line and a half long, glabrate ; the longer and widely divergent 

 lobes with the pungent stout awn about the same length, or even longer; 

 the two intermediate and much smaller pungent-pointed teeth not arising 

 from any obvious costal. Tube of the perigonium cylindraceous ; the 

 stamens some of them opposite and some alternate with the lobes. 

 Achenium and seed ovate-pyramidal. Embryo as in the following. 



* * Involucrum trigonum, 6-costatum, trifidum : bracteae spini- 

 formes. 



24. C. rigid A. P)rgmpea,primum lanata; caule Q--2-pollicari) parum 

 ramoso demum crassiore lignescente ; foliis ovatis seu obovatis subtus 

 albo-tomentosis longe petiolatis ; involucris in axillis sessilibus solita- 

 riis vel confertis bracteis elongatis aristreformibus seu lanceolatis 

 spinescenti-cuspidatis demum induratis suffultis, lobis 3 inaaqualibus 

 ovato- seu triangulari-lanceolatis cuspide spinescente recta terminates 

 tubo brevi-campanulato (majore duplo) longioribus ; perigonii tubo 

 cylindraceo basi obtuso ; staminibus 9. Acanthogonum rigidnm, Torr. 

 Pacif. R. R. 4 (Bot. Whipp.), p. 132, & 5, p. 365, & Bot. Mex. 

 Bound, p. 177 (excl. ref. "tab. 8"). — On the desert of S. E. Califor- 

 nia and the neighboring parts of Arizona and New Mexico, Bigelow, 

 A. B. Gray, Thomas, Newberry, Cooper, Parry ; also Nevada as far 

 north as Truckee Valley, Watson. The older plants horrid with the 

 tufted bracteal spines, of which the larger are about an inch in 

 length. Stamens perhaps always 9. The older involucres thin and 

 scarious between the reticulations. Cotyledons orbicular, accumbent 

 on the base of the slender curved radicle. 



* * * Involucrum tubo tereti angusto, costis obsoletis, dentibus 3 

 vel 5 cum bracteis parvulis breviter cuspidatis. Herbse exiles, 

 caule 1 - 3-pollicari demum subcymoso-ramoso. 



2o. C. corrugata. Albido-lanata ; foliis ovatis seu ovali-rotun- 

 dis longe petiolatis ; involucris demum subcymosis, lobis 3 ovato-lan- 

 ceolatis cum bracteolis herbaceis cuspide recurva apiculatis tubo subcla- 

 vato eximie corrugato (fructifero fere tuberculato) sublongioribus; tubo 

 perigonii basi attenuato ; staminibus 6 — 9. Acanthogonum corruga* 



