4] 
large flowered Datura, Abronia, Hendecandra Tecensis, and many 
others. Near Olla the first specimens appeared of a new species 
of Larrea, the first and most northern form of the shrubby 
Zygophyllacee, more abundant farther south. In the same 
neighbourhood the Mezquite tree or shrub was first met with, 
probably Algarobia glandulosa, T. and G. From this place the 
Mezquite was abundantly found down to Matamoros, but the 
specimens collected appear to indicate that there are at least two 
different species. 
On the next day,” near Sabino, an interesting Bignoniaceous 
shrub was collected for the first time, undoubtedly the Chélopsis 
of Don, which farther south appears more abundantly. Its 
slightly twining branches, willow-like slender glutinous leaves, 
and large paler or darker red flowers, render it a very remarkable 
shrub. Dr. Gregg mentions it under the name “ Mimére,” as 
one of the most beautiful shrubs of northern Mexico. The cha- 
racter given by Don, and that of De Candolle, appear defective, 
though I cannot doubt that both had our plant in view. From 
the very complete specimens obtained both by Dr. Wislizenus 
and Dr. Gregg, I am enabled to correct those errors. ; 
Near Albuquerque a curious Opuntia was observed; it evi- 
dently belongs to the Opuntia cylindracee, but has short clavate 
joints, which make the name of O. c/avata most appropriate. A 
singular plant, with the habit of a Ranunculus, but nearly related 
to Saururus, was also found in this neighbourhood among grass 
on the banks of the Rio Grande. The genus has been described 
by Nuttall from specimens collected by him in California, but 
whether his Anemopsis Californica is specifically identical with 
the new Mexican plant, remains to be seen, as this last has 
regularly six-leaved involucres, about six stamens, and is per- 
fectly glabrous. 
While the last mentioned plants indicate that we approach 
another botanical region,.we are surprised to meet here with 
Polygonum amphibium, common in the old and in the new 
world, and Cephalanthus occidentalis, so widely diffused in the 
United States. 
The famous desert, the Jornada del Muerto, furnished, as was 
to be expected, its quota of interesting plants. A Crucifera 
near Biscutella of Europe, but with very short styles and white 
flowers, was here met with abundantly. I had considered it as 
the type of a new genus, when I found in Hooker’s London 
Journal of Botany, of February, 1845, Harvey’s description of 
his new Californian genus Dithyrea, which probably must be 
made to embrace our plant as a second species. . 
