152 THE CACTACEAE. 



6. Echinomastus durangensis (Riinge). 



Echinocaclus 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 19 10. 



Illustration: Schumann, Gesamtb. Kakteen f. 61, B, as Echinocaclus durangensis. 



* 



18. GYMNOCALYCIUM Pfeiffer, Abbild. Beschr. Cact. 2: under pi. 1 and pi. 12. 1845. 



Plants globular, simple or cespitose, strongly ribbed; ribs divided into tubercles often protruding 

 at the base ; flowers campanula te 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 Echinocaclus. 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 yvfivos naked, and kciAi> 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- 

 nocalycium 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 Blti- 

 hende Kakteen 1: pi. 55), E. stellatus, and E. schickendantzii (see Schumann, Gesamtb. 

 Kakteen Nachtr. f. 29). 



Key to Species. 



A. Inner perianth-segments yellow to yellowish green. 



Ribs acute 1. G. mihanovithii 



Ribs rounded. 



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 3. G. leeanum 



Ribs 9; inner perianth-segments narrowly oblong 4. G. guerkeanum 



AA. Inner perianth-segments red, pink, or white. 

 B. Ribs hardly tubercled. 



Ovary and tube bearing few scales. 



Scales on ovary rounded 5- G. spegazzinii 



Scales on ovary acute 6. G. denudatum 



Ovary and tube very scaly 7. G. hyptiacanthum 



* Pfeiffer says: "Pfeiff. in Catal. Hort. Schelh. 1843" but this we do not credit as place of publication. 



