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nous, horizontal branches. The plant was here only 5 feet high, but 1 
grows about Santa Fe to the height of 8 or 10 feet, and continues to be 1 
found as far as Chihuahua and Parras. In the latter more favorable cli- I 
mate it grows to be a tree of 20 or 30, and perhaps even 40 feet high, as I 
Dr. W. informs me, and offers a most beautiful aspect, when covered with \ 
its large red flowers. It is evidently the plant which Toifey and James j 
doubtfully, though incorrectly , refer to Cactus Bleo H. B. K. It is nearly 
allied to Opuntiafuriosa, Willd., but well distinguished from it; and as it 
appears to be undescribed, I can give it no more appropriate name than 
O.arborescens, 5 the tree cactus, or J^oconoztle, as called by the Mexicans, 
according to Dr. Gregg. The stems of the dead plant present a most sin¬ 
gular appearance; the soft parts having rotted away, a net work of woody 
fibres remains, forming a hollow tube, with very regular rhombic meshes, 
which correspond with the tubercles of the living plant. 
The first Mammillaria was also met with on Waggon-mound, a species 
nearly related to M. vivipara of the Missouri, and also to the Texan M. 
radiosa , (Engelm. in Plant. Lindh. inedit.,) but probably distinct from 
either. Mr. Fendler has collected the same species near Santa Fe. 
On Wolf creek the curious and beautiful Zallugia paradoxa, Endl., 
looking like a shrubby Geum , was found in flower and fruit; also a (new?) 
species of Streptantkus , and an interesting Geranium, which I named G. 
pentagynum, 6 because of its having its five styles only slightly united at 
5 Opuntia arborescens, n. sp., caule ligneo erecto, ramis horizontalibus, 
ramulis cylindricis, tuberculatis aculeatissimis; areolis oblongis, brevissime 
tomentosis, aculeos 12*4^30 corneos, stramineo-vaginatos teretes undique 
porrectos gerentibus; ramulis versus apicem fioriferis; ovario tuberculato, 
tuberculis sub-20 apice sepala subulata et areolas tomentosas cum setis 
paucis albidis gerentibus; sepalis interioribus 10 13 obovatis; petalis 
obovatis, obtusis s. emarginatis; stigmatibus sub-8 paltulis; bacca flava 
^icca, ovato-globosa, tuberculata, profunde umbiliciita. f 
Mountains of New Mexico to Chihuahua, Parras; and Saltillo; flowersfin 
May and June; fruit, at least about Santa Fe, ripening the second 
year (Fendler;) in the north 5 to 10, south 20 and more feet high, 5 to 
10 inches in diameter, last branches 2 to 4 inches long; spines of the speci¬ 
mens on Waggon-mound 20 to 30 in each bunch; further south only 12 
to 20, generally fewer on the under side of the branchlets; spines horn- 
colored, with straw-colored loose sheaths, from 3 to 10 lines, generally 
about 6 lines long. Flowers purple, 3 inches in diameter; stamens red; 
fruit about 1 inch long, yellow. 
6 Geranium pentagynum, n. sp., perenne, caule erectp ramoso cum. peti- 
olis retrorso-piloso; foliis strigoso-pubescentibus inferioribus 7-, superiori- 
bus 3-5-partitis, segmentis inciso-lobatis; pedicellis binis, glanduloso pu- 
bescentibus; sepalis glandulosis, longe aristatis; petalis basi villo brevi 
instructis,. ad venas pilosiusculis, obovatis integris; filamentis ciliatis; 
ovario glanduloso; stylis ima parte solum connatis; capsula danduloso- 
pubescente. ° . 
On Wolf creek, flowers in June. Several stems 1 foot high from a large 
ligneous rhizoma; similar to G. maculatum, but easily distinguished from 
this and most other species by Oie styles being united only for i or i of 
their length; flowers of the same size, but aristas of sepals much larger; 
leaves only 2 or 2| inches wide. ' 
