SELENICEREUS. 207 



we have obtained but one flower. It j;ro\vs vigorously, giving off many long aerial roots, 

 soon reaching the top of the greenhouses. It has occasionally made small flower-buds, but 

 these soon fall. Toward the last of May 191 8, plants in Washington began to develop 

 numerous flower-buds and gave every promise of an abundance of flowers, but a very hot 

 spell occurred the first of June when the thermometer in the greenhouse rose to 1 1 4 

 Fahrenheit, and all the buds but one were killed. The plant, doubtless, needs half-shade 

 conditions. Now that we have studied a mature flower we feel justified in referring this 

 plant to Selenicereus, although it does not belong with the typical forms. The flower-bud 

 and flower are similar to those of S. vagans. The flower itself in its bell-shaped perianth of 

 short white segments, in its funnel-shaped flower-tube bearing scattered areoles, and in its 

 ovary with short stubby spines resembles very much species of Acanthocereus but in habit 

 and other respects it is very different. 



Figure 285c shows a branch with young flower-buds, 285J a terminal shoot. 



14. Selenicereus spinulosus (De Candolle) Britton and Rose, Contr. U. S. Nat. Herb. 12: 431. 1909. 

 Cereus spinulosus De Candolle, Mem. Mus. Hist. Nat. Paris 17: 117. 1828. 

 Stems clambering, 2 to 4 meters long, 1 to 2 cm. in diameter, producing numerous aerial roots, 

 light green, somewhat shining, usually angled but sometimes nearly terete; ribs 4 to 6, or some- 

 times more; spines very short, yellowish or becoming blackish; radial spines 5 or 6, with 2 reflexed 

 bristles at the base of the areole; central spine 1, rarely 2, on juvenile branches more numerous and 

 more acicular, white; flower 12 to 14 cm. long; its tube about 5 cm. long, with a few clusters of small 

 spines; outer perianth-segments narrowly oblong, 5 to 6 cm. long, acute, spreading; inner perianth- 

 segments pinkish to white, narrowly oblong, acute; stamens white, attached along the inner surface 

 of the throat; stigma-lobes white; ovary covered with clusters of spines similar to those on the tube. 



Fig. 286. — Selenicereus spinulosus. Xo.66. 



Type locality: Mexico. 



Distribution: Eastern Mexico to southeastern Texas. 



Illustration: Bliihende Kakteen 1: pi. 53, as Cereus spinulosus. 



Plate xxxviii, figure 2, shows a flowering branch of a specimen obtained by Dr. Rose 

 from Texas in 1900, which flowered in the New York Botanical Garden, April 9, 1912. 

 Figure 286 shows a growing shoot from a plant obtained by Dr. E. Palmer at Victoria, 

 Mexico, in 1907. 



15. Selenicereus inermis (Otto). 



Cereus inermis Otto in Pfeiffer, Enum. Cact. 116. 1837. 



Cereus karstenii Salm-Dyck, Cact. Hort. Dyck. 1849. 218. 1850. 



Creeping or clambering over rocks and bushes, deep green, the branches 1 to 2.5 cm. thick, 3 to 

 5-ribbed or angled, the ribs compressed, acute, undulate; old branches naked but young branches 

 bearing setae from the small areoles; areoles remote, sometimes 6 cm. apart, when young each borne 

 on a knob or elevation terminating in a subtending tip or scale ; flower just before opening 15 cm. long, 

 with a long acuminate tip, nocturnal; outer perianth-segments linear-oblong, 9 to 10 cm. long, S 

 to 10 mm. broad, yellowish green, but more or less purplish at base; inner perianth-segments oblong, 

 8 to 9 cm. long, pure white except the pinkish bases; filaments numerous, slender, weak, white; style 

 very thick, hollow, 7 mm. in diameter, pinkish, 15 cm. long; stigma-lobes numerous, greenish, 12 

 mm. long; flower-tube green, 8 cm. long, cylindric, 1.5 cm. in diameter, bearing a few scattered areoles, 



