Cephalocereus columna-trajani

Cephalocereus columna-trajani is a species of cactus from Mexico.

Description
Cephalocereus columna-trajani grows with non-branching green shoots and reaches heights of 6 to 10 meters with diameters of up to 40 centimeters. There are 16 to 26 ribs, which are almost completely divided into cusps by transverse furrows. Abundant white, silky hairs emerge from the white areoles near the tip of the shoot. The 5 to 8 downward-facing, stiff central spines are grayish and up to 8 centimeters long. The 14 to 18 white marginal spines are up to 1 centimeter long. The clearly lateral, narrow, 2 to 3 meter long pseudocephalium extends to the top of the shoot and is usually directed north. It consists of yellowish, woolly hairs 4 to 6 centimeters long.

The tubular to bell-shaped flowers are white to light yellow and have a length of up to 7.5 centimeters and the same diameter.

Distribution
Cephalocereus columna-trajani is widespread in the Mexican states of Oaxaca and Puebla, where it forms dense forests.

Taxonomy
The first description as Cereus columna-trajani was published in 1837 by Ludwig Georg Karl Pfeiffer. The specific epithet columna-trajani comes from Latin, means 'Trajan's Column' and refers to the stately nature of the species. Karl Moritz Schumann placed the species in the genus Cephalocereus in 1897. Further nomenclature synonyms are Cephalophorus columna-trajani (Karw. ex Pfeiff.) Lem. (1831), Pilocereus columnatrajani (Karw. ex Pfeiff.) Lem. (1839), Cephalocereus columna (Karw. ex Pfeiff.) K.Schum. (1894), Pachycereus columnatrajani (Karw. ex Pfeiff.) Britton & Rose (1909), Mitrocereus columna-trajani (Karw. ex Pfeiff.) Backeb. ex E.Y.Dawson (1948) and Haseltonia columna-trajani (Karw. ex Pfeiff.) Backeb. (1960).