Page:Memoir of a tour to northern Mexico.djvu/109

Rh In the following spring Dr. Wislizenus accompanied the Missouri volunteers, under Colonel Doniphan, from Chihuahua to Parras, Saltillo, Monterey, and Matamoros.

Zealous as ever, he again made large collections on this tour, but his duties as a military surgeon occupied his time rather more than the naturalist should have desired. Nevertheless his collections are very full. Fortunately Dr. Gregg accompanied the same expedition, and also made rich collections in that almost unknown region, which we may consider as the southwestern limits of the valley of the Rio Grande.

Before going into detail I will only remark here, what a reference to the map and sections will more fully present, that the country between Chihuahua and Parras has a general elevation of from 4,000 to 5,000 feet; between Parras and Saltillo it rises from 5,000 to 6,000 feet, and thence it rapidly descends towards the lower Rio Grande.

South of Chihuahua, a curious leafless Euphorbia was collected, with tuberous roots and leafless stem, nevertheless apparently a near relative of E. cyathophora. Here for the first time, Berberis trifoliata, Moric., was met with, which appears to inhabit the whole middle and lower valley of the Rio Grande, as we find it again in this collection from Monterey, and Mr. Lindheimer has sent beautiful specimens from the Guadaloupe, in Texas.

Echinocerei and Echinocacti appear in greater abundance. The rediscovery of the beautiful Echinocereus pectinatus (Echinocactus pectinatusatus Scheidw., E. pectiniferus, Lem., Echinopsis pectinata, Salm in part) is peculiarly interesting, as it furnishes the means of proving a Texan species, which has been confounded with it, to be entirely distinct. The description of the plant, (which died without producing flowers,) found in several works, as well as in the latest publication on Cactaceae, before me, of Foerster, Leipzig, 1846, was made, as Prince Salm informed me, from specimens sent from Chihuahua by Mr. Potts; it entirely agrees with my specimen from the same region. But the description in Foerster's work of the flower of a specimen in Cassel, flowering in 1843, (not