POLYPETALOUS EXOGENOUS PLANTS. 273 



filaments, inserted on the base of the petals ; style single ; 

 stigmas numerous; fruit baccate; seeds numerous, cam- 

 pylotropous, borne on several parietal placentae; albumen 

 scanty or none. 



CEREUS, Haw. 



Sepals and petals united into an elongated tube above 

 the ovary; stamens inserted on the tube; style filiform; 

 stigma many-lobed; seeds without albumen; steins elon- 

 gated, ribbed or angled, the angles bearing tufts of spines 

 and showy Jloioei's. 



C. viRiDiFLORis. Stems 3 '-6' and sometimes 8' high, 

 l'-2' in diameter; spines usually 3"-5" or nearly 6" long; 

 central spine, if present, 6"-10" long. In one specimen, on 

 some of the areolce most of the spines are purple, the cen- 

 tral one being curved upward, with a purple or Avhite tip; 

 Jloiuer 1' or less below the top, I'-l;^' long, not quite wide 

 even when fully open; jye/«Zs 2"-3" wide ; fruit 3"-6" long, 

 crowned with a withered corolla. — Dr. Engelmann, 



C. CHLORANTHUS. Stem 3-10' long, lJ'-2' in diame- 

 ter ; areolce 3-4 lines apart, not so much elongated as in 

 the last species; radial spines slender, patulous, not 

 strictly radiating, pectinate or appressed to the plant; 

 lower lateral ones the longest, inferior ones shorter, upper 

 ones shortest; no central spines are present in the young 

 plants, next 1-3 appear, and the well-developed flower- 

 bearing plants have always 5 ; the upper darker and 

 shorter ones are about 6" long, the lower ones 9"-12" or even 

 15" long ; the lowest one is the longest and regularly de- 

 flexed, so that the plant seen from above shows as many 

 rays formed by these spines as there are ribs. Flowers 

 yellowish green, always low down on the plant, forming a 

 circle round the stem; flowers an inch long, funnel- 

 shaped, not fully opening even in the bright sunshine ; 



12* 



