CACTACEA. 37 
of them are thus destroyed. My friend, Mr. Schott, of the Mexican boundary, who has lately 
returned from that desolate but rather interesting region, informs me that still further south 
this interesting plant is replaced by another not so large—but still a great cactus. This is very 
probably the one collected by Mr. Thurber, described and named by Dr. Engelmann, in Silli- 
man’s Journal, Cer. Thurbert. The pitajaya of this species, according to Mr. Schott, is the 
principal support of the Papige Indians. It is much larger, sweeter, more juicy than that of 
the Cer. giganteus. The color of the pulp is also of a much brighter red. 
In consequence of the remote and unhospitable region of this curious and interesting cactus; 
our acquaintance with it became very gradual. Dr. Englemann thinks that Baron Von Hum- 
 boldt, in his work on New Spain, must have had reference to this plant, but this is quite 
uncertain because no characteristics are given of his cacti (organos del Lunal) except size and 
edible fruit, and many other large species of both cerei and opuntiz are long and well known 
to yield them. In 1846, Major Emory first al seeds and made figures of it which, on 
being presented to Dr. Engelmann, he was i 0 pronounce it a true Cereus and at that time 
very appropriately named it. Subsequently, (winter and spring of 1852,) Dr. Parry, under 
Major Emory, visited that region, collecting spines, wood, &c., and making copious notes on 
the ground, enabled Dr. Engelmann to give a good diagnosis of it. Still Dr. Parry was unable 
to procure the flower or fruit on account of the lateness of the season. It was reserved for Mr. 
Thurber, who repassed this region in the summer of 1852, to collect complete specimens, and 
Dr. Engelmann, in a subsequent number of Silliman’s Journal, has given a complete description 
of it. (Vide Amer, Jour., Vol. XVII, 2d series, March, 1854.) To the several excellent 
accounts given of this tree by Dr. Engelmann, little of interest can be added, As noticed by 
Drs. Parry and Engelmann, the number of ribs at the base is about 12, and they ‘‘ increase 
upward, by bifurcation and addition,’’ to the largest circumference of the tree, which is about 
15-18 feet from the ground, and where also usually the few branches are given off. Here the 
ribs sometimes number 30, and from this point upward they decrease in number to 18-20. The 
wood at the base of old specimens becomes a perfect hollow cylinder, and from thence upward 
to the first branches, instead of being solid it becomes a reticulated net-work of bundles of wood 
continuing the hollow cylinder as is seen on a smaller scale in the wood of Opuntia arborescens. 
These trees in abundance give the landscape a very peculiar appearance, and from their novelty 
and entire dissimilarity to any others, at first is not only curious but pleasing, but as the eye 
becomes accustomed to it, a gradual transition takes place in ones feelings and from being 
pleasing they at last become monotonous and repulsive. This feeling, however, may be some- 
what accounted for by the surrounding sterility of the land. As far as the eye can reach in the 
vallies or on the mountains, little else but rocky boulders and the stately yet awfully sombre 
aspect of the cereus giganteus can be seen. 
OPUNTIA, Tourn. 
Subgenus 1, Pratoruntra, Englm. 
1. Opuntia Evcetmannt, Salm. At Delaware, about 170 miles west of Fort Smith, a speci- 
men of this plant was observed about four feet high. This seems to be the northern limit of a 
species which is widely spread from lower Mexico to the mouth of the Rio Grande, and on both 
sides of that river, northward and southward. In the southern regions it grows much taller 
than in the north. 
2. Op. ENGELMANNI, 8 ? CYCLODES: erecta,articulis orbiculatis, pulvillis remotis tomento griseo 
setisque stramineis rigidis inzequalibus instructis; aculeis subsingulis rectis validis compressis 
stramineis basi fuscis deffexis, adjectis seepe 1-2 inferioribus brevioribus pallidioribus; bacca 
globosa late umbilicata, seminibus late undulato-marginatis. (Plate V SEK XI. x. 9 
