r 





REVISION OF THE GENUS CEREUS MILL. 61 



B. Flowers zygomorphous. 



ft Tube and ovary with hairs or wool, but always 



with a greater or less number of often setulose 

 bristles; fruit aculeate. 



X Flowers large, with a long and slender tube. 



XIV, Eucereus Engelra. 



XX Flowers short. 



Stems slender, much elongated. 



XV. Leptocereus A. Bers; 

 Stems short, stigmata invariably green. 



XVI. Echinocereus EmrelnL 



1 



owers zygomorpnous. f t # . ,.. • •„ •, ;*• \ . 



. PeriautS'fiarKWJjC tu3nilar,Icur\y?4 J if JorAVofVan J* % 



small" em14» mtfl(Wtt>tis"*ap^Ves9ed scales; ovary and 



with 



ovary and tube 



woolly; petals mud}: I ;^ j<n£|R w pLEiSTOC actus Lem. 



2. Perianth tubular, ^§UgJitly p&Ilt«tl(fflfardf* above the ovary in 



/ 



form of an y $ with pj\tcj*it«$epaloid and petaloid, rather 

 broad perianth leaves \i**9*(Jf with stiff hairs. 



XVIII. Aporocactus Lem. 



I. CEPHALOCEREUS Pfeiffer in Otto & Dietr. 



Allgemeine Gartenztg. 6:142. (1838). — K. Sch. in 

 Engler & Prantl, Nat. Plianzenfam. III. 6a: 181. 



This subgenus is characterized by the formation of a cephalium, 

 that is to say, the lioriferous region of the plant is differentiated from 

 the rest. The ribs are divided into little Isolated mamillae surrounded 



by long hairs and spines. The flowers, which are small, rise singly 

 from the top of the mamillae. 



The reader will be best informed about this subgenus if 

 he looks at plate 3, and pages 92-93 of K. Goebel's excel- 

 lent Pflanzenbiologische Schilderungen, I Theil. (Mar- 

 burg, 1889.) 



Our knowledge of these plants is lamentably poor, and 

 material for further investigation is greatly needed. 



The following five species, all tall arborescent plants 

 from Mexico and Brazil, are enumerated by Schumann: 



Cereus (Cephalocereus) chrysomallus Hemsley. — K. Schumann, Mono- 



t^raphia. 200.* — Mexico. 



* As I do not wish to give full references to literature, I have thought 

 it advisable to mention only K. Schumann's Monographia Cactacearum, 

 1899, where all references can easily be found. 



