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1882。
The smaller straw…colored flowers alone suggest the propriety of
keeping this form specifically distinct； but even in size and color there is
an occasional tendency toward the specific character。The obliquely
obovate curved seeds resemble those of C。 viviparus。The plant densely
covered with stout ashy…gray interlocking spines is easily recognized。
62。 Cactus radiosus chloranthus（Engelm。）。
Mamillaria chloranthaEngelm。 Wheeler's Rep。 127 （1878）。
Oval to cylindrical （7。5 cm。 in diameter； sometimes 20 to 22。5 cm。
high）； with 20 to 25 gray radial spines almost in two series； 6 to 9 stouter
reddish or brownish…tipped centrals （12 to 25 mm。 long）； and yellowish or
greenish…yellow flowers 3。5 cm。 long and wide。Type： Southern Utah
specimens of both Parry and Johnson occur in Herb。 Mo。 Bot。 Gard。； but
they are all referred to C。 radiosus arizonicus； and I can find no trace of
any specimens of C。 radiosus chloranthus in the Engelmann collection。
Southern Utah； east of St。 George （Parry； Johnson）。
The plant is evidently near C。 radiosus deserti； of which variety it
seems to be the Utah representative； but in the absence not only of the type；
but even of authentic specimens； the two are kept separate； a thing fully
justified by the description。
63。 Cactus radiosus alversoni； var。 nov。
Differs from var。 deserti in its more robust and branching habit
（becoming 12。5 cm。 tall and 10 cm。 in diameter）； shorter and thicker
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North American Species of Cactus
tubercles； more numerous （12 to 14 centrals） stouter and longer （12 to 22
mm。） spines； all of which are black…tipped （the centrals black half way
down； shading into red）； and pink flowers。Type； Alverson's specimens in
Herb。 Mo。 Bot。 Gard。 and in Herb。 Coulter。
In the desert region of extreme southeastern California。
Specimens examined： Southern California （A。 H。 Alverson of 1892）：
also growing in Mo。 Bot。 Gard。 1893。
The covering of stout bushy interlocking spines is like that of var。
deserti； but the black and reddish coloration gives a decidedly different
appearance。On account of this appearance of a reddish…black brush the
plant has been popularly called 〃foxtail cactus。〃The decidedly pink
flowers were sent by Mr。 S。 B。 Parish from specimens growing in
cultivation in San Diego； and are not from the original collection of Mr。
Alverson。
64。 Cactus macromeris（Engelm。） Kuntze Rev。 Gen。 Pl。 260 （1891）。
Mamillaria macromerisEngelm。 Wisliz。 Rep。 13 （1848）。 Mamillaria
heteromorphaScheer in Salm。 Cact。 Hort。 Dyck。 128 （1850）。 Mamillaria
dactylitheleLabouret； Monogr。 Cact。 146 （1858）。
Ovate or cylindrical； 5 to 10 cm。 high； simple or branching from the
base and at length cespitose： tubercles large； loose and spreading； from a
dilated base； more or less elongated （12 to 30 mm。） and teretish （often
incurved）； the groove absent in young plants and never reaching the axil：
radial spines 10 to 17； slender and terete； or stouter and often angled；
spreading； 12 to 40 mm。 long； whitish （or more or less rose…colored when
young）； straight or a little curved； central spines 4 （or fewer in young
plants or even wanting）； spreading； 25 to 55 mm。 long； stouter； bulbous at
base； mostly black （the lowest the longest and stoutest）； straight or
sometimes curved or twisted： flowers 6 to 7。5 cm。 long and of same
diameter； deep red to purple： fruit ovate…subglobose； green； 15 to 25 mm；
long： seeds globose…obovate； yellow； and smooth。 1。2 to 1。6 mm。 long。 （Ill。
Cact。 Mex。 Bound。 t。 14 and 15）Type； Wislizenus of 1846 in Herb。 Mo。
Bot。 Gard。
Mostly in loose sand； in the valley of the Rio Grande （on both sides of
the river）； from southern New Mexico to Eagle Pass； Texas； and doubtless
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North American Species of Cactus
further down。
Specimens examined： New Mexico （Wislizenus of 1846； Wright 384；
531； of 1852； G。 R。 Vasey of 1881）： Texas （Wright of 1850； 1851； 1852；
Bigelow of 1852）： Chihuahua （Evans of 1891； Budd of 1891）： also
growing in Mo。 Bot。 Gard。 1893。
This species shows an interesting transition from Coryphantha to
Echinocactus。The woolly groove of the Coryphantha extends from the
spine…bearing areola to the axil of the tubercle； where it expands into the
flower…bearing areola。In C。 macromeris the groove extends only about half
way down the tubercle and gives origin to the flower…bearing areola on the
side of the tubercle； while in Echinocactus the flower…bearing areola
becomes adjacent to the spine…bearing areola and the flower appears at the
summit of the tubercle。
ARTIFICIAL KEY TO THE
SPECIES。
It seems impossible to make a simple artificial key that will serve as a
useful guide to each individual species and variety。Our knowledge of so
many of the species is imperfect； that no set of characters can be applied
throughout。However； as no plants are collected in such fragmentary
condition； it will be useful to construct a key based upon such characters
as are always likely to be present； even if specific distinctions are not
always reached。In many cases； species are so closely and differently
related to each other that the complete descriptions will have to be
consulted to determine the differences； and in such cases the artificial key
can only indicate the group。Even the full descriptions are very compact；
all characters not necessary for discrimination having been eliminated。No
attempt need be made to determine any species by means of the flowers
alone。In most cases more or less of the plant body will be available；
presenting spine and tubercle characters； and these are used in the
following key。The distinction between Eumamillaria and Coryphantha； on
the basis of grooveless and grooved tubercles should always be made out
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North American Species of Cactus
easily。It may be useful to suggest as a caution； however； that often
tubercles in drying develop folds which simulate grooves； and especially
is this true in quadrangular tubercles。In such cases it is necessary to restore
the original plumpness of the tubercle by boiling； before the presence or
absence of the groove can be definitely determined。The species and
varieties are indicated only by their specific or varietal names in the
following key； and the numbers refer to the serial numbers of the
synoptical presentation。Forms occurring within the United States are
marked with an 〃*〃：
I。 Tubercles never grooved。
* Central spines none。
Radials 5 to 9； stout。meiacanthus* （7）。
Radials 20 to 40。micromeris* （12）； greggii （13）。
Radials 40 to 80。lasiacanthus* （10）； denudatus* （11）。
** Central spine solitary and not hooked。
＋ Central spine longer than the radials。
Radials 7 or 8： tubercles very long （40 to 50 mm。）。longimamma （36）。
Radials 15 to 20： tubercles 6 to 8 mm。 long。eschanzieri （21）。
＋＋ Central spine shorter than the radials。
Radials 5 to 9； stout。 meiacanthus* （7）。
Radials 9 to 22。heyderi* （5）； hemisphaericus* （6）； gummiferus （8）；
gabbii （34）；sphaericus （35）。
*** Central spine solitary and hooked。
＋ Stems slender cylindric： Lower Californian。
Centrals 1； 20 to 30 mm。 long。 roseanus （23）。
Centrals 1 to 4； 20 to 50 mm。 long。 setispinus （24）。
＋＋ Stems depressed…globose to ovate。
Radials 4 to 6； rigid。 uncinatus （9）。
Radials 8 to 12。 wrightii* （15）。
Radials 15 to 30。 grahami* （19）； eschanzieri （21）。
Radials 50 to 60。 barbatus （18）。
**** Central spines more than one； and none of them hooked。
＋ Slender or sometimes stout cylind