562 ANNUAL EEPORT SMITHSONIAN INSTITUTION, 1908. 



M. gigantea, M. heesiana (pi. T), M. centricirrha, M. meiacantha, M. 

 uncmata, M. sempervivi, 31. caput-medusce, M. formosa, M. karwin- 

 skiana (pi. 14, fig. 4), and M. mutahilis. 



9. Pelecyphora. — Only two species of this interesting genus are thus 

 far known. They are very small plants, globular, hemispherical, or 

 club shaped in form, and covered with peculiar laterally compressed 

 tubercles having a very long, narrow areola, bordered on each side 

 by a row of short appressed comblike spines. Pelecyphora aselli- 

 formis^ usually growing in clusters (pi. 14, fig. 6), derives its specific 

 name from the resemblance of its tubercles to the ventral surface of 

 certain isopods, or sow bugs (Aselli). Specimens were collected by 

 Dr. Edward Palmer in May, 1905, at Zapotillo, 12 miles east of the 

 city of San Luis Potosi, where the plants are sold in the drug market 

 under the name of " peote," " peyote," or " peotillo." Another locality 

 where they are found, and which takes its name from them, is the 

 Hacienda de Peotillas, a station on the Central Railway, which con- 

 nects San Luis Potosi with Tampico. One of the specimens col- 

 lected by Doctor Palmer bloomed after it had been gathered. The 

 flower is comparatively large and of a magenta or crimson-purple 

 color, with the outer petals rose-colored and paler on the margin, and 

 the outermost sejDallike, narrowly linear and greenish white. The 

 stamens are only about one-third the length of the petals; they have 

 white filaments and orange-colored anthers, beyond which the pistil 

 projects with its greenish-yellow 4-rayed stigma. 



Pelecyphora pectinata (pi. 14, fig. 5), the pther species, which is 

 here figured for the first time, is a beautiful little plant represented 

 in the cactus house of the United States Department of Agriculture 

 by specimens collected by Dr. J. N. Rose in 1905, in the State of 

 Puebla. It is smaller than P. aselliformis, spherical at first, but at 

 length cylindrical. Unlike P. asellif ortnis it has milky juice and 

 yellow flowers, and is solitary. Its minute white spines are pectinate, 

 very much like those of certain species of Echinocereus and Mamil- 

 laria, and so closely crowded that they interlace. Plate 14, figure 5, 

 shows a young 23lant of this species enlarged 6 diameters. 



10. Ariocarpus. — This genus, called by Lemaire " Anhalonium," 

 is composed of several species of low top-shaped plants with large 

 taproots surmounted by a rosette of more or less leaflike tubercles. 

 These are made up of two parts corresponding roughly to the blade 

 and claw of certain petals. The lower portion, or claw, is flattened 

 and appressed along the stem of the plant ; the upper part, or blade, 

 is turned outward and consists of a more or less pyramidal body, the 

 upper face of which is somewhat triangular in outline. The entire 

 surface of this blade is covered with a cartilaginous coat, which, 

 together with the absence of spines, distinguishes this genus from the 



