In lieu of an abstract, here is a brief excerpt of the content:

Genus Pediocactus B. & R. The genus Pediocactus can be characterized as follows: the stems are either single or branching sparingly; flattened, spherical, or cylindrical; usually very small but in one form up to 6 inches in diameter and height. The surface of the stem is covered with small but prominent, noncoalescent tubercles , spirally arranged. Areoles are small and entirely on the tips of the tubercles, sometimes with glands present. The spines are variable. The flowers are bell- or funnel-shaped. The ovary is naked or with two or three small scales, these sometimes having a few hairs or bristles in their axils. The outer perianth segments are fringed to entire. The fruits are green at first, often changing to tan or yellowish, and then becoming dry. They are naked or have several small scales. In shape they vary from nearly spherical to almost club-shaped. The fruits are dehiscent, opening by a ring around the apex, by a lateral slit on the upper side, or sometimes rather irregularly by both of these. Seeds are black or gray, the surfaces rough or shiny but always textured when seen under the microscope. The members of this genus are once again cacti which fall between the major groups, the Echinocacti and the Mammillarias, overlapping each to some extent. Most technical discussions of these cacti have become involved with trying to balance the characters in which they coincide with the one group against the characters in which they agree with the other. This began even with Engelmann, who had the type species of this genus as an Echinocactus, but who said that this species, with some others, “forms a small section of Echinocacti with the appearance of Mammillarias named by Prince Salm Theloidei.” Although he insisted that they were still “true” Echinocacti, he repeated that they “constitute the closest and most imperceptible transition to Mammillaria subgenus Coryphantha.” To show the reasons for the divergent opinions over these cacti in the past and the way they overlap both adjacent major cactus groups while actually falling outside of either one, I will mention here the most significant of the characters involved. They share with the Echinocacti the following points: the areoles are monomorphic with the flower coming at or near the tips of the tubercles; the flowers are similar to those of the Echinocacti, the ovary often with two or three tiny scales, and occasionally these have a few bristles in their axils; the fruit becomes dry and splits open-but they differ from the Echinocacti by having no ribs and by having mucilage cells, which are not found in any recognized Echinocactus. On the other hand, they share with the Mammillarias the following characters: the stems are tubercled instead of ribbed; the ovary is sometimes naked or has only two or three scales—while differing from them by producing the flowers from a monomorphic areole at the tip of the tubercle and by having dry, dehiscent fruits. In possessing mucilage cells, as Dr. Boke has pointed out, they look genus Pediocactus 147 toward the Echinocerei. The result of all this is that this genus is left standing with those few others which are somewhat alone, outside of any of the major groups. Buxbaum has considered it significant, because of its peculiar combination of characters, as an ancestor of other groups, but other scholars have disputed his theories on this. The members of this genus can be as exasperating to the ordinary cactophile as to the taxonomist. If it is difficult to view them in the proper systematic niche, it is even harder to view them in their native habitat. They are all extremely retiring cacti. They are usually so well camouflaged in their natural environment that there are places where it is more rewarding to hunt for them by feel than by sight. And it is not easy to find their locations . With the exception of one species, they all occupy very small ranges, several only a few miles in extent, and some are noted more for their rarity than for anything else. Each is restricted to a particular soil type or geologic formation, and some are associated with one other specific plant. The one species which is more widespread is usually a high mountain inhabitant, where only hardy collectors will come across it. So these are especially challenging little cacti not seen by many people and perhaps fully appreciated by only the specialist. However, they are part of the huge group known as cacti and...

Share