Brachycereus thouarsii Weber

Cereus thouarsii Weber, Bull. Mus. Hist. Nat. Paris 5: 312. 1899.

Cereus nesioticus Schumann in Robinson, Proc. Amer. Acad. 38: 179. 1902.

Stems 6 to 10 dm. high; branches numerous, radiating and ascending, 3 to 5 cm. in diameter, entirely covered by a mass of yellow spines; ribs about 20, low, 3 mm. high; areoles 5 to 6 mm. apart; spines about 40, unequal, the longer ones about 3 cm. long, bristle-like; flower 7 cm. long; outer perianth-segments 1.5 cm. long, 2 mm. broad; inner perianth-segments longer than the outer, narrow; filaments 1 mm. long or less; fruit 2.5 to 4 cm. long, 1.3 cm. in diameter; seeds numerous, 1.2 mm. long, ellipsoid, brownish, slightly punctate.

Type locality: Charles Island, Galapagos.

Distribution: Albemarle, Abingdon, Chatham, James, Charles, and Tower Islands, Galapagos.

We have identified Cereus thouarsii Weber, by photographs of the specimens sent by Professor Agassiz to Dr. Engelmann, preserved at the Missouri Botanical Garden, and mentioned by Dr. Weber at the place of first publication.

Schumann says this species is a very peculiar one, "from its long, brown, non-pungent spines, which clothe the stem so densely that its surface is invisible. I have never before seen a species of the genus with such short filaments as in this. The petals are also uncommonly narrow."

Berger refers this species to his subsection Nyctocereus, with which it is probably most nearly related. It was named for Abel Aubert Du Petit-Thouars (1793-1864).

Illustration: Proc. Calif. Acad. Sci. IV. 1: pl. 5, as Ce-reus nesioticus.

Figure 179 shows the flower of the type specimen of Cereus nesioticus preserved in the Gray Herbarium; figure 180 shows the fruit of Brachycereus thouarsii collected by A. Stewart, preserved in the herbarium of the California Academy of Sciences.

22. ACANTHOCEREUS (Berger) Britton and Rose, Contr. U. S. Nat. Herb. 12: 432. 1909.

Weak, elongated, many-jointed cacti, at first erect but soon clambering or trailing, the joints usually strongly 3-angled, sometimes 4 or 5-angled, in one species sometimes 7-angled, the seedlings and juvenile branches not as strongly angled, with more ribs and with different spines; areoles bearing short wool or felt and several stiff spines; flowers funnelform, nocturnal, 1 at an areole; flower-tube remaining rigid after anthesis, gradually drying and remaining on the ripe fruit, green, rather slender, expanded toward the summit, bearing a few areoles similar to those of the branches, subtended by small scales; limb somewhat shorter than the tube, widely expanded; outer perianth-segments narrowly lanceolate to linear, acuminate, green, shorter than the white, inner segments; stamens not extending as far as perianth-segments, attached all along the upper half of the tube or throat; style very slender, divided at the apex into several linear stigma-lobes; fruit spiny or naked, with a thick, dark-red skin breaking irregularly from top downward; flesh red; seeds numerous, black.

This genus has a wide distribution; its species are usually found at low altitudes in semiarid regions, especially about the Gulf of Mexico and the Caribbean Sea; although occurring on the coasts of Texas and Florida and recorded from Cuba, it has not been reported from any of the other larger Antilles, but is represented on the Venezuelan and Colombian coasts and also in Central America and Brazil. It is found not only on the east and west coasts of Mexico but also in the interior.

The type of this genus is based on the Cactus pentagonus of Linnaeus. Linnaeus in his Species Plantarum cites no definite habitat for it, while his description is very meager. His earlier reference in Hortus Cliffortianus (182. 1737), although somewhat fuller, is still uncertain. It is there stated that the ribs are 5, sometimes 6. Most of the species of this genus, especially those which would have been known in Linnaeus's time, usually have 3 ribs, occasionally 4, rarely 5. The young plants and the young growth, however, often have 5 and 6 ribs, which would account for variations in descriptions of the same species.

Fig. 179.—Flower Fig. 180.—Fruit of B. thouarsii. of same species.

Fig. 179.—Flower Fig. 180.—Fruit of B. thouarsii. of same species.

Curiously enough, the type species is one of the species of Linnaeus which Miller omits in his Gardener's Dictionary (1768).

Cereus pellucidus Pfeiffer (Enum. Cact. 108. 1837), which we formerly referred to this genus (Contr. U. S. Nat. Herb. 12: 432), following previous authors, is to be looked for in Leptocereus. Both Schumann and Berger regard this group as consisting of but a single species, the former placing it with Cereus greggii in his series Acutangules, and the latter in a subsection Acanthocereus; Pfeiffer, on the other hand, recognized several species as belonging to this group; we distinguish at least 7. The name is from the Greek, meaning thorn-cereus.

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