39 
closely to Cereus, in which genus they, as well as the Behi- 
nopsis, should perhaps be included as subgenera. 
‘The species mentioned above is distinguished from all others 
known to me by its yellowish-green flowers, the others having 
crimson or purple flowers. I have named it, therefore, Echino- 
cereus viridiflorus. 
A careful examination of the seeds of numerous Cactace@, has 
indicated to me two principal divisions in that family: 1. Coty- 
ledons, more or less distinct, directed with their edges to the 
edge, (or towards the umbilicus,) and with their faces to the 
flattened side of the seed; when curved, accumbent. 2. Coty- 
ledons, mostly very distinct, foliaceous, directed with their edges 
to the faces, and with their faces to the edges of the seed (or 
towards the umbilicus); when curved, incumbent, and often 
circular or spiral. : 
The first class comprises Mammillaria, with a straight embryo; 
* and doubtless, also, Melocactus, seeds of which, however, have 
not been examined by me; and Zechinocactus, mostly with a 
_ curved embryo. The second class includes Echinocereus with a 
nearly straight émbryo, and very short cotyledons; Cereus, with 
a curved embryo, and foliaceous incumbent cotyledons, (probably 
also Lehinopsis and Pilocereus, and perhaps Phyllocactus and 
Epiphyllum ;) Opuntia, with a circular or spiral embryo, (circular 
and with a larger albumen in all Opuntia cylindracee ; spiral 
and with a much smaller albumen in all Opuntia elliptic, 
examined by me,) and very large cotyledons. Rhipsalis and 
Pereskia may also belong here, but were out of my reach. 
The flowers of all species belonging to the first class, with the 
doubtful exception of some Mammillarie, make their appearance 
on the growth of the same year. Those of the second class 
produce the flowers always upon the growth of the next preceding 
or former years. “The first class may, therefore, be, distinguished 
by the name of Cactacee parallele (from the direction of the 
cotyledons), or apiciflore (from the position of the flowers). 
The second class can be named, in a corresponding manner, 
Cactacee contraria, or lateriflore. 
Echinocereus is principally distinguished from Cereus proper 
by its low growth; its short, more or less oval stems, which are 
frequently branching at base, and thereby cespitose ; by the 
diurnal flowers, with short tubes ; by the nearly straight embryo, 
with short cotyledons. From ZHchinopsis, to which some species 
have been referred, it differs also by the short-tubed diurnal 
flowers, and by the numerous filaments being adnate to the 
lower part of the tube. The species Echinocereus inhabit Texas 
