6 UNITED STATES AND MEXICAN BOUNDARY. 
gidioribus brevioribus rectiusculis puberulis albidis, intimis 5-8 longioribus rigidis rectis 
pubescentibus basi bulbosis infra albidis sursum rufis fuscisve inaequalibus ; florum lateralium 
ovario subemerso ; sepalis 9-12 oblongo-linearibus obtusiusculis tenuiter fimbriatis ; petalis 
13-16 fere uniseriatis oblongo-linearibus obtusis vel emarginatis saepe mucronatis ; stigmatibus 
5 flavidis longe supra stamina exsertis ; bacca elongata clavata s. subcylindrica coccinea floris 
rudimentis involutis coronata; seminibus plurimis obovatis scrobiculatis nigris !ucidis, hilo 
basilari lineari. (Tab. V.) 
From Eagle Pass to Santa Rosa, Dr. Bigelow, and, according to Dr. Poselger, common on 
the Rio Grande below: fl. March to May.—Heads 1-1} inch in diameter, 1-2} inches high, 
usually covered below with young branches, and finally densely cespitose; tubercles 34-44 
lines long, dark-green ; axillee quite woolly, with several coarse twisted bristles mixed with the 
wool ; exterior hair-like spines covering the whole plant as with a coarse wool, often 6-8 lines 
long, when straightened ; interior spines slender, but stiff and pointed, 3-4 lines long, in 
young or weakly specimens, whitish, with dark tips, in robust.ones yellow at base, brown up- 
wards, and almost black at tip; flowers 7-10 lines long ; petals dirty yellowish-white, with a 
reddish streak in the middle ; fruit about 9 lines long ; seeds 0.6 line long, hard and brittle, 
very similar to the seed of the last mentioned species, only a little larger and with narrow 
hilum.—Mamillaria pusilla, from the West Indies, is so near our plant that this one must 
necessarily be referred to it ; the only difference seems to consist in the smaller number of radial 
spines (12-20) in IZ. pusilla, and in the greyish-green color of its tubercles. 
4, M. PHELLosPERMA (M. tetrancistra E. partim, in Sill. Journ. Nov. 1852): ovata seu ovato- 
cylindrica, simplex seu rarius e basi ramosa ; tuberculis ovato-cylindricis ; axillis lanatis seti- 
geris demum nudis; aculeis radialibus numerosissimis (40-60) biseriatis, exterioribus tenui- 
oribus brevioribus albis, interioribus robustioribus longioribus apice fuscatis, centralibus 3-4 
robustioribus longioribus ex basi pallidiore atrofuscis, superioribus 2-3 rectis seu uno pluribusve 
hamatis, inferiore validiore sursum hamato ; floribus versus planta apicem lateralibus. sepalis 
15-17, exterioribus ovatis obtusiusculis ciliatis, interioribus oblongo-linearibus ; nedalié sub- 
12 acuminato -aristatis ; stigmatibus 5 ; bacca obovato-clavata late umbilicata corollam marces- 
centem dejiciente tenui coccinea vix pulposa; seminibus magnis globosis rugosis, ad hilum- 
massa suberosa semine ipso majore triloba fusca arilliformi auctis. (Tab. VII.) 
Dry gravelly hills about the base of the mountains east of the Californian Cordilleras, near 
San Felipe, Dr. Parry ; also on the lower Gila, Dr. Le Conte, A. Schott : on the lower bioloende 
the Mojave, and east of the Colorado towards the Cactus Pass, ; 
. Dr. Bigelow.—T his i : 
species was first noticed by Dr. Parry, igelow.—T his interesting 
! and was described from his in Silliman’ . 
under the name of I. tetrancistra. Specimens brought home HRN Roe oo arse 
no doubt that this and several other species had been confounded ; and, moreover, that hardl 
ever all the four central spines are hooked. The original name had heim to i altered ; ea 
one selected for it indicates the peculiar corky structure of the enlarged base of the seed ea 
Our species is often simple, not rarely several stems are seen coming from one eee or an 
older stem bears young branches at its lower part; young stems almost globose older ones 
ovate, and even cylindric, 2 to 4 or 5 inches high, 14 or 2 inches in diameter - wubabolas 4—T 
lines long, not so much crowded as in the allied Species, in 8, or at most, 13 ‘atial rows. The 
axils of the young tubercles produce loose wool, with a few long spiny bristles, which dis- 
appear only after several years. In the smallest specimén before me I find 14-18 exterior 
radial spines, 4—5 lines long, and 12-16 interior ones, 5-6 lines long; in other specimens I 
