One feels nearly overwhelmed by the giant cardon of Baja California; it and the striking cirio (Fouquieria columnaris) are conspicuous elements of one of the most interesting desert floras in the world. The cardon, Pachycereus pringlei, is one of the most impressive species of Pachycereus, and Reid Moran (1998) has written a noteworthy article on the plant. Likewise, the magnificent cactus forests of southern Mexico contain members of the genus Pachycereus as well, including the massive P. weberi.

Despite the fact that members of the genus are some of the largest cacti of North America, they are poorly understood botanically. George Lindsay (1963) and Donald Pinkava (pers. comm.), for example, feel that Lophocereus should remain a separate genus, though the studies of Arthur Gibson and Karl Horak (1978,1041-1044) show that P. margin-atus is closely related to the two species usually included in Lophocereus. Whereas Franz Buxbaum (1961) placed Lophocereus and Pachycereus in separate subtribes, Gibson and Horak believe they are in the same evolutionary line, which the International Cactaceae Systematics Group has accepted, combining the genera.

Probably the species most tentatively included in Pachycereus is P. fulviceps, which has been placed in other genera


532 Pachycereus such as Mitrocereus, even Carnegiea. Gibson and Horak (1978) stated that it is nearest to Backebergia and Neobux-baumia. David Hunt (1991f), placing it in Pachycereus, said it seemed "the least of various evils to make the new combination in Pachycereus____" Further investigations of Pachycereus are in progress, especially the study of DNA sequences. It is hoped that further studies will elucidate the taxonomic position of this enigmatic species.

Sereno Watson described Cereus pringlei in 1885. He and others were fascinated by the size of the plants as well as the many uses of the cactus by Native Americans. That species and nine others were placed in the genus Pachycereus (type, Cereus pringlei — P. pringlei), described by Nathaniel Britton and Joseph Rose in 1909, the name having been used 4 years earlier by Alwin Berger as a subgenus of Cereus. The name Pachycereus is derived from the Greek pachys, thick, thus thick cereus.

Gibson and Horak (1978,1042) stated, "confusion on the generic limits of Pachycereus can be resolved only after the phylogenetic relationships of the species are clearly understood____no set of taxonomic features satisfactorily defines the genus." Nevertheless, some characters shared by the species are the absence of silica bodies in the epidermis, presence of alkaloids that form red and then black pigments when the stem is damaged, and large, shiny black seeds, each with a conspicuous ridge. Flowers are fairly small and the plants usually bloom at night in late spring and summer. Pachycereus comprises 12 species.

Pachycereus (A. Berger) Britton & Rose 1909 Cereus subg. Pachycereus A. Berger 1905 Lemaireocereus Britton & Rose 1909

Cereus subg. Lophocereus A. Berger 1905, Lophocereus (A. Berger)

Britton & Rose 1909 Anisocereus Backeberg 1938 Marginatocereus Backeberg 1942 Mitrocereus Backeberg 1942 Backebergia Bravo 1953 PterocereusT. MacDougall & Miranda 1954 Pseudomitrocereus Bravo & Buxbaum 1961

Subfamily Cactoideae, tribe Pachycereeae. Plants treelike and candelabra-like or shrubby, often becoming massive, to 25 m (82 ft) high. Stems green or bluish green, erect, stout, ribbed. Tubercles absent. Nonflowering areoles spiny; flowering areoles like nonflowering ones or different, confluent or connected byfurrows, with dense wool, and spineless. Central spines as many as 4, stout, 2-10 cm (0.8-3.9 in) long. Radial spines 20 or more, stout, 2-7 cm (0.8-2.8 in) long. Flowers usually nocturnal, short tubular, funnelform, or bell shaped, small to medium size, 4-10 cm (1.6-3.9 in) long; floral tubes scaly; pericarpels and floral tubes areoles naked, or woolly or with bristles.

Fruits oblong, fleshy, to 7.5 cm (3 in) long, densely covered with wool and bristles, dehiscing irregularly, pulp red or purple, becoming dry. Seeds helmet shaped, smooth, glossy black, large. Distribution: occurring widely throughout the southwestern United States, northern Mexico, including the Baja California Peninsula, and Honduras and Guatemala.

Pachycereus fulviceps (F. A. C. Weber ex K. Schumann) D. R. Hunt 1991

Pilocereus fulviceps F. A. C. Weber ex K. Schumann 1897, Mitrocereus fulviceps (F. A. C. Weber ex K. Schumann) Backeberg ex Bravo 1954,

Pachycereus Grandis
Pachycereus fulviceps

Pachyœreus grandis 533

Pseudomltrocereus fuiviceps (F. A. C. Weber ex K. Schumann) Bravo & Buxbaum 1961, Cephalocereus fuiviceps (F. A. C. Weberex K. Schumann) H. E. Moore 1975, Carnegiea fuiviceps (F. A. C. Weberex K. Schumann) P. V. Heath 1992

Plants at first columnar, becoming candelabra-like, much branched, to 12 m (39 ft) high. Stems glaucous green, to 8 m (26 ft) long. Ribs 11-14. Central spines usually 3 with one longer than the others, 6-7 cm (2.4-2.8 in), the shorter ones only 2 cm (0.8 in) long. Radial spines 8-12, yellowish, thin, to 1 cm (0.4 in) long. Pseudocephalium apical, covered with dense, brownish wool. Flowers open at night, arising from the mass of apical wool, funnelform, cream colored, 6-7 cm (2.4-2.8 in) long, 6 cm (2.4 in) in diameter; pericarpels and floral tubes with imbricate scales and long, dark yellow hairs. Fruits globose, covered with wool and hairs. Distribution: Puebla, Mexico.

Pachycereus gatesii (M. E. Jones) D. R. Hunt 1991 Lophocereus gatesii M. E.Jones 1934

Plants shrubby with numerous stems, often forming clumps to 2 m (6.6 ft) high and 3 m (9.8 ft) wide. Stems outcurving, becoming erect, pale olive green, 5-8 cm (2-3.1 in) in diameter. Ribs 10-15, sharply angled. Spines not distinguishable as centrals and radials, differing in upper and lower areoles. Spines of lower areoles 11-15, expanded basally, 0.5-1.5 cm (0.2-0.6 in) long. Spines of upper areoles or pseudocephalium 15-20, thin, twisted, bristle-like, to 6 cm (2.4 in) long. Flowers funnelform, coral pink, 3 cm (1.2 in) long and in diameter; pericarpels and floral tubes scaly. Fruits globose, red with red pulp, dehiscing irregularly, 2.5 cm (1 in) in diameter, with broad naked scales. Distribution: Todos Santos northward and Margarita Island, Baja California Sur, Mexico.

Pachycereus gaumeri Britton &Rose 1920 Anisocereusgaumeri (Britton & Rose) Backeberg 1942, Pterocereus gaumeri (Britton & Rose)T. MacDougall & Miranda 1954 Pterocereus foetidus!. MacDougall & Miranda 1954, Anisocereus foetidus (T. MacDougall & Miranda) W. T. Marshall 1957, Pachycereus foetidus (T. MacDougall & Miranda) P. V. Heath 1992

Plants treelike, unbranched or sparsely branched, to 8 m (26 ft) high with trunks to 1.5 m (4.9 ft) high. Stems long, erect, slender. Ribs 3-4, very acute, almost winglike, with widely spaced areoles. Spines about 10, gray or reddish black, to 5 cm (2 in) long. Flowers open at night, cylindrical to funnelform, greenish white, foul smelling, 8.5-9.5 cm (3.3-3.7 in) long; pericarpels and floral tubes covered with fleshy, leaflike scales reflexed at their tips and with some wool and a few bristles. Fruits globose, light red. Distribution: Yucatán and Chiapas, Mexico. Pachycereus gaumeri is not well known.

Continue reading here: Pachycereus granis Rose 1909

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