4-", 



their bases communicating with the sheath to the rear of the tip and ad- 

 jacent to it. When the sheath separates from the spine (which happens 

 very early), these ends of the fibers at the base of the cones are slightly 

 lifted from the surface of the spine, forming sharp barbs extending back- 

 ward on the surface near the tip. This conical barbed structure is likewise 

 common to the sheathless, flat-joint Opuntias, and extends even to the 

 minute and much-dreaded bristles of the same genus. It is this property 

 of conical arrangement that makes the prickly pear group the terror of 

 all who have made its acquaintance. 



While many of the characters brought to light in these investigations 

 are artificial as must naturally result in tissues so responsive to envi- 

 ronment as epidermal structures, the constancy of character within 

 the same species, together with the requisite variation in features pre- 

 sented by different species, can not but be of service to those engaged in 

 a critical study of the family. 



The genus cactus. By E. M. Fisher. 



The genus Cactus, as it stands at present, consists of about 350 species 

 and varieties from North America, of which only twenty-five species and 

 seven varieties have been reported from the United States. All these 

 forms are small, ranging from one half to three inches in diameter, and 

 are distinguished by their disconnected tubercles. 



In this paper it is proposed to consider briefly the history of the genus, 

 and the classification of its species. To give an accurate and satisfactory 

 history of this genus or any of the genera of Cactaceae is a very difficult 

 thing, because of the meager descriptions and the scarcity of early litera- 

 ture. Taking 1753 (the date of the first edition of Linnaeus' " Species Plan- 

 tarum") as our datum-line, and tracing both backwards and forwards, we 

 reach the following results: In this first edition of the "Species Plan- 

 tarum," Linnaeus published all the Cactacea> with which he was acquainted 

 under one genus, Cactus, which he subdivided into four groups called Echi- 

 nomelocactus (subrotund), Ceril (erect, angular), Cerii (creeping with lateral 

 roots), and Opuntia (jointed, compressed, proliferous). Previous to this 

 (1737), in the first edition of the Genera Plantarum, Linmcus published 

 Cactus as embracing the genus Cercus of Jussieu's Acta Gallorum (1719), 

 and Opuntia and Melocactus of Tournefort's Institutions (1719). Melocaclus 



