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specimens as well。Aside from the fact that the Mexican specimens are apt
to be more robust； I can discover no difference whatever。 For discussion of
relationships see under C。 scolymoides。
46。 Cactus radians pectenoides； var。 nov。
Differs in its cespitose habit； fewer （16 or 17） and stouter spines （8 to
9 mm。 long）； and its larger and longer （10 mm。） less deeply grooved
tubercles。Type in Herb。 Coulter。
San Luis Potosi。
Specimens examined： San Luis Potosi （Eschanzier of 1891）。
47。 Cactus corniferus（DC。） Kuntze； Rev。 Gen Pl。 260 （1891）。
Mamillaria corniferaDC。 Rev。 Cact。 111 （1829）。 Mamillaria
impexicomaLem。 Hort。 Monov。 Cult。 5 （1839）。 Mamillaria cornifera
impexicomaSalm。 Cact。 Hort。 Dyck。20 （1850）。
Globose； 7。5 cm。 in diameter； simple： tubercles oblong…ovate； 2 cm
long； crowded； the younger axils woolly： radial spines 15 to 26； rigid and
horny； curved or sometimes straight； reflexed； bulbous at base； yellowish
（whiter with age） and with dark tips； very sharp； 10 to 12 mm； long； the
central one much stouter； darker； slightly deflexed； 12 to 16 mm long；
sometimes wanting： flower unknown： fruit obovate； red； 2 cm long： seeds
reddish； angular； smooth； 2 mm。 long。Type unknown。
From San Luis Potosi to southern Mexico。
Specimens examined： San Luis Potosi （Parry of 1879； Eschanzier of
1891）： also specimens cultivated in Mo。 Bot。 Gard。 in 1892； growing in
same garden in 1893。Mamillaria impexicoma Lem。； afterwards reduced to
a variety； was based upon fewer radial spines and no central。As the central
is occasionally wanting in connection with the most numerous radials； and
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present with the fewest； such a form would have to be separated solely on
the absence of the central spine； and even in the original description of
impexicoma the central spine is only said to be 〃sometimes wanting。〃It
has been impossible for me to separate the forms。 It should be said that the
fruit and seed characters given above were taken front a specimen whose
few radials and no centrals would undoubtedly refer it to impexicoma。As
yet we are ignorant of the flower of C。 corniferus。 For discussion of
relationships see under C。 scolymoides。
＋＋ Central spines 1 to 4。
48。 Cactus scolymoides （Scheidw。） Kuntze。 Rev。 Gen。 Pl。 261
（1891）。
Mamillaria scolymoidesScheidw Allg。 Gart。 Zeit。 ix。 44 （1841）。
Globose or ovate； 5 to 7。5 cm。 high。 subsimple： tubercles conical； 10 to
16 mm。 long； the upper elongated； incurved and imbricate： radial spines 14
to 20； straight or often recurved； white or horny； 10 to 20 mm。 long （the
upper the longer）； central spines 1 to 4； longer （18 to 32 mm。）； more dusky；
curved； the upper ones turned upwards and intermixed with the radials； the
lower one stouter； longer； and curved downwards： flowers 5 cm。 long： fruit
unknown。Type unknown。
From the Pecos River； western Texas； westward into southern New
Mexico； and southward into Chihuahua and San Luis Potosi。
Specimens examined： Texas （Hays of 1858）： New Mexico （Bigelow of
1853）： Chihuahua （Wislizenus of 1846）： also specimens cultivated in St。
Louis in 1858。
Specimens collected by Mrs。 Anna B Nickels across the Rio Grande
from Laredo； Texas； and showing neither flower nor fruit； seem to
intergrade between C。 scolymoides and C。 scolymoides sulcatus。The habit
is that of the former； the tubercles are those of the latter； while the spines
are somewhat different from either。The number of central spines in these
specimens is very hard to determine； as on the adult tubercle they all
assume a radial position。The usual adult arrangement is an apparent
absence of central spines； 10 to 12 rigid； spreading and more or less
recurved radials （increasing in length from the lowest）； which are mostly
white or the upper more or less dusky； and above； just behind the radial
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North American Species of Cactus
row； 2 or 3 stout recurved…ascending spines； which are white with tips
more or less reddish…black； one of the spines usually much stouter and
longer than the others。This form may represent a distinct species； but it
seems very unsafe to add species to the C。 scolymoides group without the
fullest information。
Prince Salm…Dyck refers C。 scolymoides to 〃M。 daimonoceras Lem。
Cact。 gen。 nov。； p。 5；〃 but no mention of such a name can be found in the
work referred to。Labouret refers C。 corniferus to the same name and
reference。If 〃M。 daimonoceras〃 was anything more than a garden or
herbarium name used by Lemaire I have been unable to find it； and Dr。
Engelmann's notes indicate that his search met with the same result。It is
possible that the name was applied loosely to this assemblage of closely
related forms that seem to cluster about C。 corniferus。
A most perplexing question of relationship is presented by the forms
that have been called pectinatus； scolymoides； sulcatus （calcaratus）；
Echinus； and the Mexican forms radians； impexicomus； corniferus。It may
be that they are all merely varieties of one strong polymorphic type； but
our knowledge of corniferus is so incomplete； and material of other forms
is so scanty； that I can not venture to make such an assertion。However； it
seems probable that radians； pectinatus； scolymoides； sulcatus and
Echinus all have green fruit； while in impexicomus and corniferus it is
red。It has also seemed proper to merge radians and pectinatus； also
impexicomus and corniferus； and to refer sulcatus to scolymoides as a
variety。These seven forms are thus reduced at least to four species。
49。 Cactus scolymoides sulcatus （Engelm。）。
Mamillaria sulcataEngelm。 Pl。 Lindh。 246 （1845）； not Pfeiff。 （1848）。
Mamillaria strobiliformisMuhlenpf。 Allg。 Gart。 Zeit。 xvi。 19 （1848）； not
Scheer （1850）。 Mamillaria calcarataEngelm。 Pl。 Lindh。 195 （1850）。 Cactus
calcaratusKuntze； Rev。 Gen。 Pl。 259 （1891）。
Differs in its smaller size； proliferous and much more cespitose habit；
the dilated base of the more spreading tubercles； fewer （8 to 12） radial
spines； usually a single central spine （wanting in young plants） and
somewhat larger flowers。（Ill。 Cact。 Mex。 Bound。 t。 74。 fig。 1； seeds）Type；
Lindheimer of 1844 in Herb。 Mo。 Bot。 Gard。
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Texas； from the Brazos to the Nueces。
Specimens examined： Texas （Lindheimer of 1844； Fendler 34； Wright
of 1850； 1854； 1857）： also specimens cultivated in St。 Louis in 1845； 1848；
1853； 1859。
This seems to represent the northeastern extension of the species； and
doubtless it will be found merging into it south and west of the
Nueces。Curiously enough one of the prominent distinctions originally
given was the single central spine； while in the type specimen there occur
tubercles with more than one central。
50。 Cactus echinus （Engelm。） Kuntze； Rev。 Gen。 Pl。 260 （1891）。
Mamillaria echinusEngelm。 Syn。 Cact。 267 （1856）。
Globose or subconical； 3。5 to 6。5 cm。 in diameter； simple： tubercles
terete； conical； grooved above； 10 to 12 mm。 long： radial spines 16 to 30；
pectinate； straight or little curved； rigid and appressed （interwoven with
neighboring clusters）； ashy…white （often dusky at apex）； 8 to 12 mm。 long；
the uppermost longer （12 to 20 mm。）； central spines 3 or 4； the upper ones
turned upward and intermixed with the radials； the lower one very stout；
15 mm。 long； subulate from a very thick bulbous base； straight （rarely
slightly curved） and porrect （deciduous in old specimens）： flowers 3 to 5
cm。 long： fruit oval； elongated； about 2 cm。 long； green： seeds elongated…
obovate。 brown and smooth； about 1。8 mm。 long。 （Ill。 Cact。 Mex。 Bound。 t。
10）Type； the Wrigh