lizenus collected thriving plant and flowers, and Dr. Gregg the ripe fruit. It is distinct from the other Echinocacti found in those regions by the membranaceous very thin sepaloid scales on the tube of the flower and the juicy glabrous fruit, in which respect it resembles my E. setispinus from Texas; E. texensis, Hpfr., has a juicy fruit, covered with woolly and spiny scales; E. Wislizeni and others have a dry fruit, covered with hard scales.
My Opuntia frutescens (Plant. Lindh. 1. c. p. 245) which had been collected by Mr. Lindheimer along the Colorado and Guadaloupe rivers, in Texas, was also found south of Chihuahua by Dr. Wislizenus, and again along the route near Parras, and below Monterey. The suggestion made in the Plant. Lindh., that it may be a southern variety of O. fragilis of the Upper Missouri, has proved to be erroneous, as they belong to quite distinct sections of the genus Opuntia; O. frutescens, together with O. vaginata, (vide note 18,) is one of the Opimtiae cylindraceae graciliores, and is apparently nearly related to O. leptocaulis DC, but is easily distinguished by its strong, white, single spines, while O. lept. has 3 short blackish bristles.
Agave Americana, with several relatives, was found in abundance on this part of the route; Argemone Mexicana, white, yellow, or rosecolored, was frequently met with; Samolus ebracteatus occurred in moist places so far inland, and on such elevations, while before it was only known as a litoral plant; Malvaceae, Oenotherae, Asclepiadaceae, Giliae, Solaneae, Justiciae, shrubby Labiatae, were collected of many different species; but the great characteristic of the country were the shrubs forming the often impenetrable thickets, called "chaparrals." They are mostly spinous,
before me 4 inches in diameter, 3 inches in height; the large recurved spines, especially the stoutest central one, which is of a bluish horncolor, with a brown point, and is curved and bent downward like a large fang, cover the whole surface of the plant, and give it a very pretty appearance. Lower radiating spines 6 to 10, upper 12 to 15 lines long; upper central spines 12 to 18 lines long, but lower stouter one only 10 to 12 lines in length. Flowers described from the shrivelled specimens found on the living plant; about 1 inch in length, and probably pale red. I have little doubt that some fruits collected in the same region (about San Lorenzo) by Dr. Gregg belong to this species; the fleshy oval berry is 10 or 12 lines long, covered with the same auriculate thin scales which we find on the flowers, and crowned with the remnants of the flower; seeds black, much compressed, somewhat rough, albumen considerable, embryo curved, cotyledons short obtuse. This is a very remarkable plant, and approaches in shape some mammmillaria; the tubercles which form the interrupted ribs are sideways compressed, have a tomentose groove on their upper edge, which ends in a regular axillary depressed areola, like that of a true mammillaria ; but the scaly ovary and the curved embryo prove it to be an Echinocactus. The specimen brought here by Dr. W. died soon after it arrived, as many of those collected in April and May during the flowering season, though only two months on the road, while those collected the year before between August and November, which had been packed up for eight or ten months, mostly do very well now. Dr. Gregg's seeds, however, have germinated well.
