152 THE CACTACEAE. 
6. Echinomastus durangensis (Riinge). 
Echinocactus durangensis Riinge, Hamb. Gartenz. 46: 231. 1890. 
Simple, ovoid, about 8 cm. long, 7 cm. in diameter; ribs 18 to 21, low; areoles white-woolly when 
young, but without wool when old; radial spines 15 to 30, the lower ones shorter than the upper, more 
or less incurved, white except the black tips, 1.5 cm. long; central spines 3 or 4, a little longer than the 
radials, acicular, about 2 cm. long; flowers and fruit not known. 
Type locality: Not cited, but Schumann reports it only from Rio Nazas, west of Villa 
Lerdo, Durango, Mexico. 
Distribution: Zacatecas and Durango, Mexico. — 
This species is similar to Echinomastus unguispinus, but not so large, with more slender 
and lighter-colored spines, none of them strongly recurved. We know it only from a 
specimen collected in Zacatecas by Dr. Elswood Chaffey in 1910. 
Illustration: Schumann, Gesamtb. Kakteen f. 61, B, as Echinocactus durangensis. 
q ) 18. GYMNOCALYCIUM Pfeiffer, Abbild. Beschr. Cact. 2: under pl. 1 and pl. 12. 1845.* 
Plants globular, simple or cespitose, strongly ribbed; ribs divided into tubercles often protruding 
at the base; flowers campanulate to short-funnelform, from upper and normally from the nascent 
areoles, usually large for size of plant, white, pink, or rarely yellow; flower-tube bearing broad 
scales, these with naked axils; fruit oblong, red so far as known, scaly; seeds cap-shaped or dome- 
shaped, brownish, tuberculate. . 
The species of this genus which were treated by Schumann are found in his subgenus 
‘Hybocactus of Echinocactus. We recognize about 23 species, all from South America, east 
of the Andes and chiefly from Argentina, with a few species from Bolivia, Paraguay, and 
Uruguay. The generic name is from yuprds naked, and xé\vé bud, referring to the glabrous 
flower-bud. 
The genus was originally based on three species of which G. denudatum was the first, 
and this is taken by us as the generic type. Heynhold (Nom. 2: 103. 1846) uses the three 
names of Pfeiffer. | 
The tubercles on the ribs have an enlargement more or less conspicuous just below 
the spine-areole which Schumann calls a “chin.” So far as our observation goes this is 
present in all the species, although it is very small in G. saglione, and it may be of con- 
siderable diagnostic importance. By this character plants belonging to species of Gym- 
nocalyctum can be referred generically when not in flower. 
The flower in this genus, as in the other genera of this tribe, normally comes from the 
center of the plant, borne on nascent areoles; but sometimes, especially in greenhouse 
plants, the flowers of some are lateral and borne on old areoles as in E. gibbosus (see Blii- 
hende Kakteen 1: pl. 55), E. stellatus, and E. schickendantzii (see Schumann, Gesamtb. 
Kakteen Nachtr. f. 29). 
KEY TO SPECIES. 
A. =, perianth-segments yellow to yellowish green. 
Sacute......... eee eee ee ; ichit 
oF 1. G. mihanovic 
Ribs 11 to 14; inner perianth-segments broadly oblong. 
Ribs very definite; tubercles broader than high........................... 2. G. netrelianum 
_Ribs low, rather indefinite; tubercles subglobose.....................00-. 3. G. leeanum 
Ribs 9; inner perianth-segments narrowly oblong...........0..0......0..0.. 4. G. guerkeanum 
AA. Inner perianth-segments red, pink, or white. 7 i 
B. Ribs hardly tubercled. 
Ovary and tube bearing few scales. 
Seales on ovary rounded...........00. 0000 cece eeceee eee... 5. G. spegazzinit 
Scales on ovary acute........00..00.0.0...00.0000 ss 6. G. denudatum 
Ovary and tube very scaly... vie pe coat en ee te cee tves ceded sceevincee leds 7. G. hyptiacanthum 
“Pfeiff. in Catal. Hort. Schelh. 1843” but this we do not credit as place of publication. 
* Pfeiffer says: 
