REVISION OF THE GENUS CEREUS MILL. 



59 



critical revision. Everybody will perceive this who reads 

 carefully the descriptions of the flowers of the plants at 

 present united under Pilocereus by Schumann and Weber. 

 These flowers differ from each other in important details. 

 There remains nothing to maintain the genus in its old 

 form, except the hairy areoles of the stems, a character 

 which is not even the same in all. The greater number of 

 these plants are rare in gardens, and many have never 

 flowered, so that our knowledge of them is very insufficient 

 and does not permit any further critical study. 



Equally with Pilocereus, Cephalocereus of Pfeiffer and 

 Schumann has also to be reunited with Cereus, as it is 

 well connected by two other subgenera with the rest of the 



genus. 



Before speaking of each subgenus, I give an analytical 

 synopsis, which will help the reader to understand the 

 matter at once. 



SYNOPSIS OF THE SUBGENERA OF CEREUS. 



I. Flowers rising from a distinct cephalium. 



I. Cephalocereus PfeifE 



II. Flowers not from a cephalium, several from one and the same areole. 



A. Areoles of the flowering part differing from the rest, more closely 



set, with numerous long setulose bristles; flowers reddish or 

 yellowish, stamens included; fruit scaly. 



II. Lophocereus A. Berg. 



B. Areoles of the flowering part not different, with spines, but with- 



out setulose bristles; flowers wiiite, stamens exserted; fruit 



smooth. 



III. Myrtillocactus Console. 



III. Flowers single from the areoles. 

 A. Flowers actinomorphous. 





1. Flowers short, more or less campanulate or tubular. (See 



also Nos. XV and XVI, with short flowers!) 



a. Flowers tubular. 



with 



f Ovary densely woolly; petals short, spatulate; 

 fruit very woolly and prickly. 



IV. Pachycereus A. Berg. 



