170 



THE CACTACEAE. 



Plate xxv, figure 1, shows the top of a plant received from the Missouri Botanical 

 Garden in 1904, which flowered in the New York Botanical Garden, June 23, 1915; figure 

 2 shows a flowering piece of a plant sent to the New York Botanical Garden from Guaymas, 

 Mexico, by Dr. Rose in 19 10. Figures 241 and 242 show flowers of a plant collected by Dr. 

 MacDougal at Torres, Sonora, in 1902. 



2. Rathbunia kerberi (Schumann) Britton and Rose, Contr. U. S. Nat. Herb. 12: 415. 1909. 



Cereus kerberi Schumann, Gesamtb. Kakteen 89. 1S97. 

 Cleistocactus kerberi Gosselin, Bull. Mens. Soc. Nice 44: 33- i9°4- 



Columnar, somewhat branched, 2 meters high; ribs 4, compressed; radial spines about 16, 

 subulate; central spines 4, stouter than the radials, 4.5 cm. long; flowers 12 cm. long; outer perianth- 

 segments linear-lanceolate, rose-colored, reflexed; stamens exserted; scales on the ovary lanate in 

 the axils. 



Type locality: On Volcano of Colima, Mexico. 



Distribution: Known only from the type locality. 



Dr. Rose saw flowers of this plant in the herbarium of the Botanical Garden at Berlin 

 in 1912 and noted that it was a Rathbunia; otherwise it is known to us only from descrip- 

 tion. In transferring it to Rathbunia (loc. cit.) we associated specimens with it from Sinaloa 

 and Tepic, Mexico, which now appear better referable to Rathbunia alamosensis, although 

 the flowers are longer than in typical specimens (8 to 10 cm. long) and somewhat curved. 



31. ARROJADOA gen. nov. 

 Stems low, much branched, cylindric; roots fibrous; ribs numerous, low, straight; areoles close 

 together, bearing small acicular spines ; flowers diurnal, borne in a pseudocephalium at the top of 

 stem or branch, small, red or pink, resembling in color and size that of a large Cactus (Melocactus), 

 nearly cylindric, the tube short; perianth-segments in several rows, short, erect; stamens and style 

 included; fruit a small, oblong, naked, juicy berry; seeds small, black. 



This is a peculiar genus, with no very close allies. The original reference of its two 

 species to Cereus is not warranted by any taxonomic considerations, for the structure, 

 origin, and shape of the flowers and fruit are quite different. In size and form the flower is 

 similar to Lophocereus, but here the resemblance ends. Its terminal pseudocephalium is 

 most characteristic, for instead of remaining as a permanent crown of the plant it forms a 

 lateral collar for the new joint which is projected through its center. 



The name is in honor of Dr. Miguel Arrojado Lisboa, the present superintendent of 

 Estrada de Ferro Central de Brazil, to whom Brazil is indebted for the extensive botanical 

 exploration of the semiarid regions made a few years ago. 



The genus contains 2 species, of which Cereus rhodanthus is selected as the type. 



Key to Species. 



Branches short and thick, 2 to 4 cm. in diameter 1. A. rhodanlha 



Branches long and slender, 1 to 1.5 cm. in diameter 2. A. penicillata 



1. Arrojadoa rhodantha (Gurke). 



Cereus rhodanthus Giirke, Monatsschr. Kakteenk. 18: 69. 1908. 

 Low, i to 2 meters long, at first erect, afterwards branching and clambering; joints short, 

 cylindric, 2 to 4 cm. in diameter; ribs 10 to 13, low; areoles small, approximate, usually less than 1 

 cm. apart; spines at first brown, in age white, the central ones similar to the radials except a little 

 longer, when young accompanied by some long cobwebby hairs; bristles at the tops of the joints 

 long, brown; flowers solitary at the upper areoles, forming in clusters of 12 to 14 at the tops of 

 branches, pink, rigid, 3 to 4 cm. long; ovary and lower part of tube naked; uppermost scales and 

 perianth-segments similar, obtuse; stamens numerous, included; fruit red, oblong to obovate, about 

 2 cm. long. 



Type locality: Caatinga de Sao Raimundo, Piauhy, Brazil. 



