Thompson — Four New Plants from Mexico. 25 



have the flowers in panicles, the ultimate branches being 

 more or less evident secund spikes or secnnd racemes — in 

 this latter case the flowers very short pedicelled. The 

 individual flowers, in all their parts, show characters 

 common to both genera. ^* Carpels erect" as attributed 

 to Sedastrum is true in the freshly opened flower (the 

 styles are usually slightly curved outward) but as the 

 carpels mature they become quite strongly divergent 

 (with incurved styles), as much so as in many species of 

 Sedum. In view of the above observations it seems in- 

 advisable to separate the species under Sedastrum from 

 the genus Sedum. The great range of variation between 

 the species of Sedum as it is now recognized requires that 

 the generic characters be quite elastic, — quite more than 

 sufficient to include the species of Sedastrum. With this 

 conclusion the generic position of our plant is quite clear. 



EXPLANATION OF ILLUSTRATIONS. 



Plate VII. — Ipomoea grandidentata. Inflorescence and characteristic 

 leaf, natural size. 



Plate VIII. — Echeveria fimdriata. Rosette of foliage, natural size. 



Plate IX. — Echeveria flmbriata. Inflorescence, natural size. 



Plate X. — Sedastrum pachucense. Flowering plant, natural size. 



Plate XI. — Sedastrum Hemseleyanum, Rose. Flowering plant, nat- 

 ural size. 



Plate XII. — Sedum versadense. Flowering plant, x%. 



Issued April 21, 1911. 



