Cacti of Texas and Neighboring States: A Field Guide

Genus Wilcoxia

Genus Wilcoxia B. & R. The genus Wilcoxia was erected by Britton and Rose in 1909. Some earlier writers had included its members in Cereus and some in Echinocereus. Since 1909 the species in the genus have been dealt with in various ways. Berger placed them in the genus Peniocereus, while Benson returned both of these genera to the genus Cereus, and others have considered each of these a subgenus of that large genus. Whatever they have concluded about the genus, all recent writers have agreed that while these species seem to form a rather good grouping, the separation of the genus as such from other genera is not as clear-cut as they would like. Most say that any final word on the genus will have to await further investigation. With this word of caution about its status, I use the genus in the way most authorities are using it at the present time. Five species in this genus are usually recognized. They are almost entirely Mexican, only one species coming into the United States at all, and that one only into southern Texas. They are also inconspicuous cacti. In form they are very slender-stemmed, sparingly branched bushes. The stems, about 5/8 inch or less in diameter, grow very long but are weak, so the plants seldom attain much size unless they have trees or shrubs to recline upon. If growing in a thicket, they clamber over the other plants, some species then becoming up to 3 yards or more long. But the slender stems are usually well hidden among the branches of the supporting plants. Each individual grows from a cluster of tuberous roots which provide the water storage for these cacti, whose stems are too slender to handle that function adequately. The spines are very short, 1/4 inch or less long, and are appressed to the stems. There is also more or less hair on the areoles. The flower is large and beautiful, bell-shaped or funnel-shaped, but with a short tube. It is reddish to purplish in color and diurnal. The ovary surface is scaly, woolly, and covered with bristly or hairlike spines which remain on the fruits. The seeds are black. By way of summarizing the differences between the genus Wilcoxia and those genera closest to it encountered in our area, I can list the following points: genus Wilcoxia differs from the genus Echinocereus by having much more slender stems, by its clambering habit, by never being caespitose, by having fascicled, tuberous roots, by producing its flower from within its spine areole instead of from a rupture of the stem epidermis just above the areole, and by the difference of seed form. Wilcoxia differs from the genus Peniocereus by having even more slender stems with eight ribs where that genus has only three to six ribs; by having fascicled tubers while that has a single extremely large taproot; by producing red to purple flowers with short 80 genus Wilcoxia perianth tubes, which open during the day, instead of white or very occasionally rose-colored flowers with long tubes, which open nocturnally; by having fruit with wool and bristles instead of with rigid spines; and by the difference in seed form. Wilcoxia poselgeri (Lem.) B. & R. (Benson: Cereus poselgeri) Pencil Cactus, Dahlia Cactus, Sacasil roots Cluster of to 6+ spindle-shaped, tuberous roots, to about 4 in. long, about 1 in. diameter. stems Long, very slender, round with 8 very low, inconspicuous ribs, 1/4—5/8 in. thick; upper parts green, lower parts becoming brown and woody; sparingly branched to form weak bush, when supported, to 3—4 ft. tall. areoles Very small, very close together; with some white wool. spines 9—12 very slender radial spines about 1/16—3/16 in. long; perfectly flat against surface of plant; white or gray; 1 central about 1/4 in. long, turned upward against upper radials; white, whitish tipped with brown, or all dark. flowers On sides of stems, very near tips; funnel-shaped, 11/2—2 in. wide by 2—21/2 in. long, deep pink; outer petals narrow with greenish midribs and pink edges; inner petals broader but still linear, sharply pointed, deep pink or rose-colored shading to lighter edges; pale yellow stamens; 8 long green stigma lobes; ovary surface has reddish scales and dense covering of long wool and black-and-white hairlike bristles; open about noon and close before night, usually for 2—3 days. fruits Oval, becoming nearly dry...