382 
with short or foliaceous cotyledons,—Hechinopsis Zuce. (1837); Cephato- 
cereus Pfeitt, (1838); Cephalophorus Lem, (1838); Pilocereus Lem. (1839) ; 
Hehinonyctanthus Lem. (1839); Hehinocereus Engehn. (1848); Cleistocac- 
tus Lem, (1861). 
It is often perplexing to distinguish between the low forms of Cereus and Hchino- 
cactus in the absence of complete material, But the fact that the flowers of Mchino- 
cactus are developed just above the nascent spine-bearing areoliw, and those of Cereus 
just above the fully matured bunches of spines, results in making the tlowers of the 
one terminal and of the other lateral. Even in the absence of flowers it is very 
seldom that the position and age of flower-bearing areole can not be easily deter- 
mined, 
Our information with regard to the large species of Cereus,even those which are 
of economic value throughout Mexico, is very scanty. In 1869 Dr. Engelmann 
visited Dr. Weber in Paris, who had collected Cacti extensively in central and south- 
ern Mexico, and had made a large aceumulation of notes. These notes are now to be 
found among those of Dr. Engelmann, and although often incomplete, and even 
incoherent in the characterization of species, | have ventured to include them. 
I, ECHINOCEREUS. Stems oval or cylindrical: seeds tuberculate: em- 
bryo straight. 
* Stems oval: ribs numerous (10 to 21): spines numerous (12 to 30), pectinate. 
+ Flowers green: central spines 7 to 3 cm. long; radials not crowded, 
1. Cereus viridiflorus Engelm. Pl. Fendl. 50 (1849). 
Echinocereus viridiflorus Engelm. Wisliz. Rep. 7 (1848), 
Subglobose, simple or sparingly branched, 2.5 to 7.5 em. high: ribs 
13, acute, scarcely interrupted: radial spines 12 to 18 (with 2 to 6 seta- 
ceous upper ones), straight and strictly radiant, 2 to 6 mm. long, later- 
als longest and reddish brown, the rest white (rarely purple); central 
none or a single stout, straight or curved spine (rarely a second more 
slender one) 12 to 14 mm. long, variegated purple and white: flowers 
2.5 em, long and wide, greenish-brown outside, yellowish-green within; 
petals obtuse: fruit elliptical and greenish, 10 to 12 mm. long: seeds 1 
to 1.2 min. long, tuberculate.—Type, Wislizenus 514 of 1546 in Herb, 
Mo. Bot. Gard. 
From the Laramie Mountains of southern Wyoming, southward 
through Colorado to eastern New Mexico and the high plains of north- 
westerr Texas. The most northern Cereus. 
Specimens examined: WYOMING (/ayden of 1856, at base of Lara- 
mie Mts.): CoLORADO (Hall & Harbour 69 of 1861; Scoville of 1869; 
Greene 132; Martindale of 1879; Jones 103): NEw Mexico (Fendler 
278; Wright, near Santa Fe; Herans of 1891): TEXAS ( Wislizenus 514 
of 1846; Wright of 1849; Bigelow of 1853): also specimens cultivated 
in Mo, Bot. Gard. in 1861; and growing in same garden in 1892 and 
1893. 
This and the following variety are exceedingly variable as to color of radial spines 
and presence of one or two centrals. Some clusters of spines may be all red, others 
all white, others variegated; and in the spring the bright purple and white spines 
are far more showy than the inconspicuous greenish tlowers, the lines of color often 
