low shrub, 6-18 inches high; joints 1-2 inches long; tubercles 4-5 lines long; spines not over an inch in length. Flower apparently yellow, about 1 inches in diameter and somewhat persistent on the fruit. Fruit very shallow, saucer-shaped, with few large seeds. Var. B. is 4 or 5 feet high; joints 8-10 inches long; interior spines 1-1 inches long. Fruit globose or even ovate, with 25 pulvilli. Seeds the same in both.

37. O. SERPENTINA, E. in Sill. Journ. 1852: erectiuscula seu subprostrata; articulis elongatis cylindricis; tuberculis ovatis; aculeis 7-9 albido- seu rufido-vaginatis; flore flavo extus rubello; bacca subhemisphærica late et profunde umbilicata villosa aculeatissima.

Near the sea-coast about San Diego, California. — Sometimes 4-5 feet high, but often prostrate; joints 6-12 inches long; spines less than one inch long. Flower cup-shaped, 1 inch wide. Fruit apparently like that of the last species, but "long woolly" and with fewer pulvilli, also often crowned with the persistent flower. Seed unknown; said to be large. — Closely allied to the foregoing species. Can this be Nuttall's Cactus Californicus (Cereus, Torr. & Gr. Fl.), with cylindric branches, yellow flower, and spiny fruit?

tt Decidua arborescentes: articuli tumidi, perfragiles: tubercula depressa flores purpurei: baccæ sæpissime steriles, proliferæ.

38. O. PROLIFERA, E. 1. c.: ramis divaricatis; articulis ovatis seu ovato-cylindricis perviridibus versus ramorum apicem congestis; tuberculis obovato-oblongis prominulis; aculeis 8-10 obscuris stramineo- seu rufo-vaginatis, singulo centrali, cæteris patulis ; flore rubro; bacca ovata aculeolata plerumque sterili prolifera.

ets.

On arid hills about San Diego, California, forming extensive thickStems 2-4, and sometimes even 6-7, inches in diameter, 310 feet high; joints 3-6 inches long and 14-2 in diameter; tubercles about 6 lines long; spines 6-14 lines long, the lower ones shorter. Flowers red, salver-form, 11⁄2 inches in diameter.

39. O. FULGIDA, E. in B. C. R.: ramis divaricatis; articulis ovatis seu ovato-cylindricis glaucescentibus versus ramorum apicem congestis; tuberculis ovato-oblongis prominulis; aculeis 5-9 subæqualibus laxe vaginatis undique stellato-porrectis; flore purpureo parvo; bac ca ovata inermi vix tuberculata; seminibus parvis rostratis.

Mountains of Western Sonora: fl. July and August. Plant 5-12 feet high; joints 3-8 inches long; tubercles rather elongated, 6-7

lines long; spines 1-1 inches long, hiding the whole plant with their lustrous sheaths. Flower about one inch or less in diameter. Fruit fleshy, 1-1 inches long, usually sterile. Seeds smaller than in any other Opuntia examined, 1-1 lines long.

40. O. BIGELOVII, E. in P. R. R.: ramis erectis adscendentibusve; articulis ovato-cylindricis pallide virescentibus congestis; tuberculis subhemisphæricis depressis confertis ; aculeis 6-10 robustioribus et totidem gracilioribus inferioribus; ovario tuberculato; bacca tuberculata subinde (sterili ?) aculeolata; seminibus parvis.

On Williams's River, of the Californian Colorado. -Stem 3-4 inches thick and 10-12 feet high; the branches forming a dense contracted head, with joints 2-6 inches long; tubercles 3-4 lines long; larger spines about an inch long, smaller ones 4-7 lines long.

The three foregoing species represent this subsection west of the California mountains, and east of them both south of the Gila and north of it, and seem to be well distinguished from one another by the characters indicated.

tit Cristata: frutescentes vel arborescentes: articuli cylindrici: tubercula plerumque cristata prominula: flores purpurei: baccæ inermes seu rarius aculeatæ.

41. O. WHIPPLEI, E. & B. in P. R. R.: caule erecto seu rarius subprocumbente divaricato-ramoso; articulis cylindricis; tuberculis ovatis confertis ; aculeis brevibus cinereo- seu stramineo-vaginatis, 1 – 4 majoribus, 2-8 brevioribus deflexis vel radiantibus; flore rubro; bacca subglobosa tuberculata flava inermi; seminibus regularibus. Var. a. LEVIOR: humilior, aculeis paucis deflexis.

Var. B. SPINOSIOR: elatior, aculeis plurimis radiantibus.

From Zuni westward to Williams's River (a.), and south of the Gila (3.): Al. in June. The first state is from a few inches to 3-6 feet high; the second forms small trees 8-10 feet high. Joints - inch in diameter; tubercles about 5 lines long; spines very variable, between 3 and 9 lines long. Flower (of var. B.) 14-14 inches in diFruit about an inch long.

ameter.

42. O. ARBORESCENS, E. in Wisl. Rep. (O. stellata, Salm.): arborescens; ramis verticillatis horizontalibus vel pendulis ; articulis verticillatis cylindricis; tuberculis cristatis prominentibus; aculeis 8-30 stellato-divaricatis; flore purpureo magno; bacca subhemisphærica tuberculato-cristata flava inermi; seminibus regularibus.

From north and east of Santa Fé and the Llano Estacado, to Zuni; extending southward deep into Mexico: fl. May-July. - Northward 5-6, south 10-20 or more, feet high; easily characterized by the horizontal and verticillate branches, etc.

43. O. ACANTHOCARPA, E. & B. in P. R. R.: arborescens; ramis alternis adscendentibus; articulis cylindricis; tuberculis elongatis; aculeis 8-25 stellato-divaricatis; bacca subglobosa tuberculata aculeata; seminibus multangulatis.

Mountains of Cactus Pass, between Santa Fé and the Western Colorado. Stems 5-6 feet high; branches few, alternate, and separating from the stem at an acute angle. Joints (as in the preceding) 4-6 or 8 inches long, about 1 inch in diameter; tubercles 9-10 lines long; interior spines 1-1 inches, exterior ones 4-10 lines, long. Spines of fruit on the depressed tubercles 3-6 lines long. Seeds large, unlike those of any other Opuntia seen by me.

44. O. MAMILLATA, A. Schott in litt., B. C. R.: arborescens, divaricato-ramosissima; articulis crassis abbreviatis perviridibus; tuberculis tumidis; aculeis 4-6 brevibus plerisque deflexis; flore parvo purpureo; bacca obovata inermi; seminibus parvis.

Sonora, on the Sierra Babuquibari, in fertile soil: fl. July and August. Stems 5-6 feet high; joints 3-4 inches long, 1 inches in diameter; the swelling tubercles very prominent; spines 3-9 lines long, sometimes almost wanting. Flowers an inch or less in diameter.

45. O. THURBERI, E. in B. C. R.: frutescens, erecta; articulis cylindricis gracilibus elongato-tuberculatis; aculeis 3-5 brevibus divergento-deflexis; flore miniato.

Bacuachi, Sonora: fl. June. Much more slender than any species yet enumerated in this subgenus. Joints inch in diameter; tubercles 9 lines long; spines 3-8 lines long, the lowest one the stoutest. Flower 1 inches in diameter.

**Monacantha: lignum densum: articuli graciliores obscure tuberculati aculei singuli: flores flavi seu rubri; semina plus minus marginata.

46. O. WRIGHTII, E. 1. c.: frutescens, erecta; articulis cylindricis gracilibus elongato-subtuberculatis; aculeis subsingulis porrectis vel subdeflexis; flore miniato.

On steep mountain-sides, from the Limpio to the Pecos, and in Northern Mexico: fl. June and July. Shrub 2-4 feet high, 1-1}

inches thick. Joints 4 lines in diameter; tubercles depressed, 7-9 lines long; spines 8-10 lines long. Flower about 1-1 inches in diameter.

47. O. ARBUSCULA, E. 1. c.: arborescens, erecta, capitato-ramosissima; articulis læte viridibus elongato-subtuberculatis; aculeis subsingulis porrectis vel subdeflexis; flore flavo-virescente.

On the Lower Gila, near Maricopa village: fl. June. A truly arborescent form, with a solid trunk of 4 or 5 inches in diameter, 7 – 8 feet high; joints 2-3 inches long, about 4 lines in diameter; tubercles indistinct, about 6 lines long; spine 9-12 lines long, often with 1 or 2 smaller ones under it. Flower 1 inches in diameter.

48. O. VAGINATA, E. in Wisl. Rep. (partim): frutescens, erecta ; ramis erectiusculis; articulis subtuberculatis; aculeis subsingulis; bacca obovata tuberculata coccinea.

Albuquerque, New Mexico, and southward. - Shrub 3-5 feet high, 1-1 inches thick; joints 3-4 lines in diameter; tubercles rather distinct, 6-9 lines long. Fruit 8-9 lines long. Seed about 2 lines in diameter. Perhaps a stout form of the next species.

49. O. FRUTESCENS, E. in Pl. Lindh. 1845: frutescens, erecta; ramis erectiusculis; articulis teretibus; aculeis subsingulis; flore parvo virescente; bacca obovata haud tuberculata coccinea.

Var. a. LONGISPINA: articulis nascentibus stipitatis; aculeis validioribus longioribus laxe vaginatis.

Var. B. BREVISPINA: articulis nascentibus sessilibus; aculeis gracilioribus brevioribus arcte vaginatis.

From the Colorado of Texas to Matamoras and Saltillo, westward to Sonora and the Californian Colorado: fl. June to August. — Var. a. is the usual Western form; B. occurs only in Texas and Eastern Mexico. - Shrub 3-5 feet high, stem 1-14 inches thick; joints 23 lines in diameter; indistinct tubercles 3-5 lines long; spiñes in a. 1-2 inches, in ß. 4–6 lines, long. Flower 7-9 lines in diameter. Fruit 5-9 lines long. Seeds few, usually 14 lines in diameter.

50. O. TESSELLATA (O. ramosissima, E. in Sill. Journ. 1852): frutescens, erecta seu diffusa, divaricato-ramosissima; articulis gracilibus tessellato-tuberculatis cæsiis; tuberculis 5-6 angulatis planis inermibus seu aculeum elongatum paucosque minutos gerentibus; flore purpurascente parva; bacca setosissima sicca.

Valley of the Lower Colorado from Sonora to the California moun

tains fl. May to September. Stems 2-6 feet high, at the base. 1-3 inches thick; joints 3-3 lines in diameter, ashy gray; the singular flattened and angular tubercles 2-3 lines long; spines 112 inches long, crowded together at the upper end of each year's growth, very loosely sheathed. Flower purple, half an inch in diameter. Fruit 9-10 lines long, covered with reddish-brown bristles. Seed 2 lines or less in diameter.

** The material for the present study of our Cactaceae is not as full as would have been desirable in the examination of so difficult a family. Hence it may sometimes have happened, that what I have endeavored to distinguish as species are forms which properly belong together; or I may have combined as one species incomplete specimens of quite distinct plants. The fear of confusing heterogeneous plants under one name, and the desire to indicate to future explorers all the different forms known to me, combined to induce me to proIceed as I have done.

For those who naturally may be horrified at the idea of 117 species of Cactaceae in a territory where, a few years ago, scarcely half a dozen were known, I will indicate how the mass of material may be comprehended under fewer types.

Of Mamillaria the species 1-9 are quite distinct, and can in no manner be united; 10-12 might perhaps be considered as forms of a single species; 13-17 are all very distinct; 18 and 19, 20-23, 25 and 26, 27 and 28, may possibly be forms of only four types, instead of 10, as I have enumerated them, thus referring my 30 species to 22 types.

In the genus Echinocactus the following species might be united: 1 and 2, 7 and 8, 9 and 10, 12 and 13, 14 and 15, — leaving 15 instead of 20 types.

The following species of Cereus will perhaps bear reduction: Nos. 1 and 2, 3 and 4, 5-7, 10 and 11, 12 14, 16 and 17, 18-22 (though some of them, of which I do not even know the flowers, may prove to belong even to different sections !), 23 and 24, cing my 31 species to 18 types.

thus redu.

Opuntia is a still more difficult genus, and mistakes are here most easily made. Many of them are as yet very incompletely known; and without being able to compare a great number of living specimens