PACHYCEREUS. 



75 



Figure 1 10 shows a flower drawn from an herbarium specimen collected by Edward 

 Palmer at San Luis Potosi, Mexico, in 1905; figure in is from a photograph of the plant 

 used as a hedge near the City of Mexico. 



I 



... .'/t&jBes-j— -a 



-Pachycereus marginatus used as a hedg 



8. Pachycereus ruficeps (Weber). 



Pilocereus ruficeps Weber in Gosselin, Bull. Mus. Hist. Nat. Paris n: 509. 1905. 

 Cereus ruficeps Vaupel, Monatsschr. Kakteenk. 23: 27. i9 ! 3- 



Stout, columnar, 15 meters high, from a simple trunk, 3 to 4 dm. in diameter, but branched 

 above; branches erect; ribs about 26; young spines all reddish; radial spines 8 to 10, about 1 cm. long, 

 rigid, grayish; central spines 1 to 3, the longest 4 to 5 cm. long, porrect or deflexed; flowers at the top 

 of the plant, campanulate, 5 cm. long, the ovary and tube bearing small chartaceous scales, these 

 with small tufts of felt and a few yellow bristles in their axils; stamens numerous, arranged in 2 

 series; style stout, light flesh-colored; stigma-lobes 7 to 9; fruit small, not edible; seeds small, brown- 

 ish, shining. 



Type locality: Near Tehuacan, Mexico. 



Distribution: Oaxaca, Mexico. 



This species has been described rather fully by Roland-Gosselin, but we are still in 

 some doubt as to its relationship. 



Dr. Rose collected flowers of it in 1905, but these were confused with specimens of 

 Cephalocereus macrocephalus, which seems to indicate that the two species grow together. 



When Dr. Rose was at the Museum of Paris in 19 12 he was given a flower from the 

 type collection made by M. Diguet. 



Illustration: Bull. Soc. Acclim. France 52: 58. f. 17, as Corns ruficeps. 



