he confusion has arisen from the fact that in both the publications of 1856 the description in the Rep。 Mex。 Bound。 is referred to； and in that report the plant is fully described as 〃sp。 nov。〃 However； the publication of the Boundary Report was long delayed on account of the preparation of the plates； and in the meantime both the publications of 1856 had appeared； in each one of which the species is distinctly characterized and reference made to the description in the forthcoming Boundary Report。 As between the two publications of 1856 the Syn。 Cact。 （Proc。 Amer。 Acad。 iii。 259） was evidently distributed first。
8。Cactus gummiferus （Engelm。） Kuntze。 Rev。 Gen。 Pl。 260 （1891）。
Mamillaria gummifera Engelm。 Wisliz。 Rep。 21 （1848）。
Hemispherical； 7。5 to 12。5 cm。 broad and 6 to 10 cm。 high： tubercles 12 to 15 mm。 long： radial spines 10 to 12； the lower stout； with dusky apex； 12 to 15 mm。 long； twice or thrice as long as the whitish setaceous upper ones； central spine （sometimes two） shorter （about 4 mm。）； stout； dusky and porrect： flowers 3 cm。 long； reddish…white； brownish…red outside： fruit unknown。 （Ill。 Cact。 Mex。 Bound。 t。 9。 figs。 18…20） Type probably lost； as no specimens could be found in the Engelmann Herbarium。
Chihuahua； near Cosihuiriachi。
So far as can be discovered； this species has not been collected since the original Wislizenus collection of 1846…47。 The plants were cultivated by Dr。 Engelmann and made to bloom； showing the flowers to be larger and darker colored than in the rest of the group； from which the species also differs in its more robust habit； its very unequal radial spines； and the occasional occurrence of two centrals。
** Central spine hooked。
9。Cactus uncinatus （Zucc） Kuntze； Rev。 Gen。 Pl。 261 （1591）。
Mamillaria uncinata Zucc。 in Pfeiff。 Enum。 34 （1837）。 Mamillaria bihamata Pfeiff。 in Otto and Deitr。 Gart。 vi。 274 （1840） Mamillaria adunca Scheidw。 （1845…1849？）。 Mamillaria depressa Scheidw。 （1845…1849？）。
Usually globose （occasionally depressed or even subcolumnar）； 5 to 6 cm。 in diameter （doubtless becoming larger）： tubercles 8 to 10 mm。 long； woolly in the upper axils： radial spines 4 to 6； rigid； 4 to 6 mm。 long； the upper one stouter than the rest and sometimes shorter； reddish…brown and horny； straight or slightly curved； the remainder straight and white with dusky tips； central spine stout and horny； reddish…brown； 7 to 10 mm。 long： flowers greenish…white or tinged with red： fruit unknown Type unknown。
Entirely Mexican； reported from Chihuahua to Saint Luis Potosi。
Specimens examined： San Luis Potosi （Gregg of 1848； Parry 268； Eschanzier of 1891）： Chihuahua （Wislizenus of 1846…47； also Chihuahua specimens cultivated in the Jacoby Garden in 1856 and 1857）。
The variations observed in this species do not seem sufficient for the establishment of varieties。 The type form seems to have been globose； with 4 radial spines and a stout central one。 The depressed forms with 6 radials and a more slender central represent var。 spinosior Lem。 （M。 depressa Scheidw。）； and the subcolumnar forms with 6 radials （the upper one of which is somewhat curved） and a stout strongly hooked central represent var biuncinata Lem。 （M。 bihamata Pfeiff。） Such combinations of characters； however； do not hold； as any one of the plant body forms may display any one of the spine characters referred to。
B。 Tubercles terete。
* Central spines none： mostly simple globose plants； with very numerous straight whitish setaceous radials。
10。 Cactus lasiacanthus （Engelm。） Kuntze； Rev。 Gen。 Pl。 259 （1891）。
Mamillaria lasiacantha Engelm。 Syn。 Cact。 261 （1856）。
Globose or ovate globose； 2 to 2。5 cm。 high and 1 to 2 cm。 broad： tubercles 4 mm。 long； about 2 mm。 in diameter； with naked axils： spines 40 to 60； in many series； very unequal； 2 to 4 mm； long； white and pilose； the upper exterior usually longer than the rest； the innermost usually much shorter： flowers 12 mm。 long； whitish or pinkish （petals with red median band）： fruit 1 to 2 cm。 long： seeds about 1 mm。 long； blackish and conspicuously pitted。 （Ill。 Cact。 Mex。 Bound。 t。 3）。 Type； the specimens of Wright in Herb。 Mo。 Bot。 Gard。
From western Texas （〃west of time Pecos； on low limestone hills； among herbage〃） to Arizona and Chihuahua。 Fl。 April； May。
Specimens examined： Texas （Wright 121； also of 1852； Parry of 1852）： Arizona （Miller of 1881）： Chihuahua （Pringle 213； 250；258）： also specimens cultivated in St。 Louis in 1852 and 1855。
11。 Cactus lasiacanthus denudatus （Engelm。）。
Mamillaria lasiacantha denudata Engelm。 Cact。 Mex。 Bound。 5 （1859）。
Larger； 2。5 to 3。5 cm。 in diameter； with longer tubercles （5 to 6 mm。）； and more numerous （50 to 80） longer （3 to 5 mum。） spines which are naked or nearly so。 （Ill。 Cact。 Mex。 Bound。 t。 4） Type； Wright specimen in Herb。 Mo。 Bot。 Gard。
From western Texas （with the species） to Coahuila。
Specimens examined： Texas （Wright of 1852）： Coahuila （Palmer of 1880）。
In the Syn。 Cact。 Dr。 Engelmann merges this variety with the species； and has been followed in this by subsequent writers； but the characters seem so （distinctive that its varietal rank has been restored。
12。 Cactus micromeris （Engelm。） Kuntze； Rev。 Gen。 Pl。 260 （1891）。
Mamillaria micromeris Engelm。 Syn。 Cact。 260 （1856）。
With depressed top and very rarely branching； 1 to 3。5 cm。 in diameter： tubercles very small （about 1 mm。 long） and wart…like； crowded； shedding the spines with age and giving the base of the plant a tuberculated appearance： spines from white to ashy…gray； 1 to 3 mm。 long； in young plants and on lower tubercles of adult plants about 20； equal and radiant； on flower…bearing tubercles 30 to 40； stellate…porrect in every direction； the 6 to 8 upper ones two to four times longer than the rest （4 to 8 mm。）； clavate toward the apex and acute （the clavate top at length deciduous）； intermixed with loose wool of about the same length and forming a small tuft on the top of the plant which includes and partly hides flowers and fruit： flowers whitish to light pink； almost central； very small （6 mm。 in diameter）； much reduced （3 to 5 sepals； 5 petals； 10 to 15 stamens； 3 stigmas）： fruit 8 to 12 mm。 long： seeds 1。5 mm。 long； black and shining。 （Ill。 Cact。 Mex。 Bound。 t。 1 and 2。 figs。 1…4） Type； the specimens of Wright in Herb。 Mo。 Bot。 Gard。
On naked mountain tops and sides； extreme southwestern Texas （Val Verde County to El Paso） and southward into Coahuila and Chihuahua。
Specimens examined： Texas （Wright 227 of 1849； also of 1852； Nealley of 1892）： Coahuila （Bigelow of 1853）： Chihuahua （Pringle 212）： also growing in Mo。 Bot。 Gard。 1893。
The plants densely covered above with delicate ashy…gray spines and with naked tuberculate base are readily recognized。 It still remains an open question whether the flowers are developed from the axils of tubercles of the same season or the last ones of the preceding season。 Dr。 Engelmann inclined to the latter view； as all the other characters of the plant associate it with the 〃lateral…flowered〃 species； and in the absence of definite observation we have retained it there。 If the nearly central flowers indicate that they are produced from growth of the same season the species would seem to be allied to Coryphantha； in which group its small flowers and small tubercles would be anomalous。
13。 Cactus micromeris greggii （Engelm。）。
Mamillaria micromeris greggii Engelm。 Syn。 Cact。 261 （1856）。
Larger （2。5 to 5 cm。 in diameter） and becoming oblong； with larger globose…ovate tubercles （2 to 2。5 mm。 long）； fewer rigid spines all radiant （interior 5 to 7 shorter and stouter； 1 to 2 mm。 long； the outer 15 to 18； 3 to 4 mm。 long）； and fruit 1。5 to 2 mm。 long。 （Ill。 Cact。 Mex。 Bound。 t。 2。 figs。 5…8） Type； Gregg 508 in Herb。 Mo。 Bot。 Gard。
Mountain ridges near Saltillo； Coahuila。 Said by Budd to occur within the southern borders of Pecos County； Tex。
Specimens examined： Coahuila （Gregg 508； Palmer of 1880）。
It is a question whether this variety does not merely represent an older and better developed plant than those upon which the species is based。 Mr。 Harry I。 Budd； who has made extensive collections of Texan and Mexican Cacti for the market； reports that it is impossible to separate sharply the variety from the species in the field； and regards the difference merely as one of age。 Unfortunately； only living material of the species could be examined； but its characters seem well sustained even in the most vigorous plants； some of which reach the size of the variety。 Through this variety the species is brought very near the following：
14。 Cactus bispinus。
Mamillaria microthele Muhlenpf。 Allg。 Gart。 Zeit。 p。 11 （1848）； not Lem。 （1838）。
Differs from the last form （var。 greggii） chiefly in its cespitose habit； much larger tubercles； and two unusually stout and short central spines （fide Engelmann； who examined specimens in Coll。 Salm…Dyck）。
Credited to Mexico in general； but said by Budd to occur within the southern border of Pecos County； Tex。
** Central spines present and one or more hooked。 ＋ Mostly globose and simple plants （occasionally somewhat cylindrical）。
15。 Cactus wrightii （Eng