1900] BRIEFER ARTICLES 349 
_ amples here cited may be fairly taken, I think, as types, as without 
- exception they agree in general characters. 
Echinocactus Wislizent Engelm.— Plants about 7.5% high and 3.5 
tog in diameter gave the following results. Three or four main 
Mots, 10 to 12" thick, branch out horizontally from beneath the plant, 
taper but slightly, are sinuous and much branched at the tips, in such 
3 amanner as pretty thoroughly to cover the ground about the plant 
| Nithina radius of 2.4". The fine rootlets are very numerous, gener- 
_ alyturning upward. In no place does this set of roots run much more 
_ than to™ below the surface. Just beneath the plant are a few small 
“ati passing almost directly. downward, tapering very rapidly, and 
vith numerous branchings penetrating to the depth of scarcely 30™. 
Opuntia fulgida Engelm.—An arborescent form. A specimen 
- tbout 15% high, considerably branched, showed, as in the above case, 
| “veal long slender roots with fine branches, running horizontally 
_ $0 10 below the surface, and covering an area with a radius of 30 
. about the plant. In a plant of O. fulgida mamillata (Schott) Coulter, 
} Yhich was washed by a small torrent, these roots appeared above 
‘ Jobat in many places. In both of these specimens a few quickly 
7 '’apering roots were demonstrated at the base of the plant, passing 
- diteetly downward to the depth of about a foot. 
Opuntia Whipplei Engelm. showed a similar state of affairs. 
A Platopuntia (O. angustata Engelm.?) possessed much the same 
Cters. out roots and 
alee by innovation * but the chief roots are to be found attached 
5 oldest living joint. At this point a double system can be seen, 
the surf a couple of large roots, horizontal and but slightly age 
“and one or two much smaller roots passing downward with 
«“Mpid branching, 
: ole - iil Engelm.—This plant thrives on x0 Lee 
a system is modified somewhat by conditions of soil an 
dons In the specimen examined the roots which passed directly 
ard came very quickly i ‘th a flaky bedrock, into the 
y in contact with a 7 ae 
oe Which they sent their branches, sometimes causing eae 
- beet do — Although these roots seemed to pass ——. ge 
re directed hee hold was exceedingly firm. The aggre € 
Mlace, by: —" entirely up the slope, sometimes gaseneee sae 
‘Tov often descending to some little depth to avo 
| *Y,J.W.: Vegetal dissemination in Opuntia. Bor. Gaz. 20: 356. 1895: 
