440 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
° Spines more numerous, 2 to 5 cm. long, diva- 
ricate, or the two lowest appressed, some- 
what flattened, whitish, or at least pale. 
Fruit oblong to clavate, large............. 24. O. engelmanni. 
. Fruit spheroidal, small.................... 32. 0. 
ascending, usually only the one or two terminal 
joints erect, mostly under 30 cm. high, sometimes 
forming irregular beds of an area of several square 
meters. 
Spines mostly white or pale, at most yellow or yellow- 
ish brown at base or tip; joints mostly small, 15 
cm. long or less, of various shapes. 
Plants small, usually consisting of only a few joints, 
these 6 or 7 cm. long; spines slender, 3 to 5 cm. 
long; glochids yellow, very long on the edges 
cyclodes. 
of young joints; flowers red...................31. O. filipendula. 
Plants larger, often of numerous joints 8 to 15 cm. 
long; spines various; glochids usually not promi- 
nent, except on old joints, then very numerous; 
flowers yellow. 
Joints spiny only on the upper marginal areoles. .25. 0. 
Joints spiny almost throughout. 
Spines mostly 2 to 4 cm. long (plants resembling 
O. polyacantha, but with pulpy fruit); 
some of the joints nearly orbicular, 8 to 10 
cm. long; seeds larger, about 6 mm. in di- 
ameter; roots fibrous..................... 26. O. 
Spines longer, 3 to 6 cm. long, slender; joints 
narrowly obovate, 10 to 15 cm. long or even 
larger; seeds smaller, 3.5 to 4 mm. in diame- 
ter; roots sometimes tuberous............. 27. O. 
Spines darker, stouter, light brown or dark brown, 
sometimes lighter at the tip or with age; joints 
mostly about 15 cm. long, sometimes larger, obo- 
vate, often broadly so, or the older joints almost 
orbicular. 
Spines yellowish brown at the base, lighter toward 
the tip, the lateral spines usually lighter col- 
ored and more or less appressed................ 28. O. 
Spines darker colored, mostly dark brown, widely 
spreading, 5 to 6 cm. long, or even more, rarely 
if ever appressed. 
Glochids on old joints very abundant and large, 
10 to 12 mm. long; plant of the southern part 
of the State. 0.0.2.0. 0000. 29. O. 
Glochids less numerous and shorter; plant of the 
north-central part of the State.............. 30. O. 
stenochila. 
cymochila. 
tenuispina. 
toumey/. ' 
chihuahuensis. 
camanchica. 
In the treatment here given there is some uncertainty about several of the species, 
the degree and character of the doubt being expressed in the notes following the 
separate species, which should be consulted. 
Just what Opuntia phacacantha brunnea Engelm. is we are unable to determine. It 
is probably a form very similar to that here referred to O. toumeyi Rose, but should be 
an erect, spreading plant, similar to the species. 
