24 
of Cactaceae by Dr. N. L. Britton and Dr. J. N. Rose, now in 
press for the Carnegie Institution of Washington. 
KEY TO THE GROUPS AND THE SPECIES 
Plants with essentially uniform joints, or sometimes with the joints of ae main 
stem more or less fused into a flattened or subterete trunk; | 
or narrowed at the base. 
Stems and branches with firmly attached pata fruits 
rsistent; plants typically freely floweri 
Mature spines w ae or uniformly gray. 
$s with armed joints (joints or whole plants 
sometimes individually unarmed); joints 
of the branches relatively small (less 
than 2 dm. long): berries purple or red. 
Mature see prostrate, or erect and 
ushy diffuse, the joints not fused 
into a eae I. TORTISPINAE. 
Mature plants erect, with the joints of the 
stem fused into a subterete trunk which 
ig divided above into few or many 
spreading branches. II. AMMOPHILAE. 
Plants with unarmed joints (joints sometimes in- 
dividually weakly armed with white spines): 
joints of the branches relatively large (over 
2 long): berries red or orange, said to be 
mee yellow. TIT. Ficvus-INDICAE. 
Mature spines vellow, dark-red, or brown, uniform, 
discolored, or banded. 
Mature spines vellow, or slightly discolored, 
stout and more or less curved, or very short 
and mostly hidden in the areolae, not closely 
spirally twisted: berries narrowly pyriform 
too id. IV. DILLENIANAE. 
ae. spines red or brown, banded in our 
bein closely spirally twisted: berries 
indish pyriform, conspicuously turgid. V. ELATIORES. 
Stems and ae with loosely attached joints, these 
readily separating when shocked or touched: fruits 
early deciduous: plants not freely flowering, but freely 
ropagating - the easily scattered joints. VI. CURASSAVICAE. 
Plants with elongate terete continuous stems, or stem and 
main branches, — branchlets of thin. Hat, dilated joints: 
berries broadly rounded at the base. VIL. BRASILIENSES. 
{. Tortispinae 
Plants prostrate, the stem and branches often forming de- 
pressed mats of joints: joints dark-green. 
