Page:Memoir of a tour to northern Mexico.djvu/100

[ 26 ] the name of O. vaginata, as the straw-colored loose sheaths of the long remarkable. A new Echinocereus was also collected here, which on account of its dense covering with small spines, I have named E. dasyacanthus. I have in cultivation one of the largest specimens, seen by Dr. Wislizenus, which is one foot high. In this neighborhood Opuntia Tuna, Mill., was seen for the first time, and this is perhaps the most northern limit of that extensively diffused species, as well as of Agave americana, another common Mexican plant. Both were found in greater perfection near Chihuahua, and from there constantly down to Monterey and the mouth of the Rio Grande; the Opuntia appears to extend also high up in Texas.

Together with these a Dasylirion, perhaps the same as the Texan species, was found here, and afterwards again near Saltillo.

From El Paso to Chihuahua, the road lies in part through a dreadfully arid sandhill district where a peculiar Martynia was observed, and