80 Standley : Some Echinocerei oe New Mexico 



In many of the descriptions of this group the color of the 

 spines is given as white, changing to ashy-gray or dark-gray. No 

 such change was observed in any of the plants examined. Indeed, 

 the young spines are often darker in color than the older ones. 

 The spines at the base of the plant are frequently discolored by 

 soil and water and this may have been the foundation for the 

 statements in the descriptions mentioned. 



The spines in these Echinocerei occur in areolae along the ridges 

 of the plant The arrangement of the spines in the areolae varies 

 slightly in different plants and sometimes in the same plant. There 

 are usually four central spines, sometimes more, which are com- 

 monly longer than the others. Around these, about the edge of 

 the areola, are a number of radials. For convenience I have 

 divided these into three groups. At each side of the areola are 

 three or four long spines which I have called laterals. Above 

 these are two or more very small spines which are often decid- 

 uous with age ; these are the superior radials. Below the laterals 

 are three or four spines, longer than the superior ones, which may 

 be called inferior radials. 



In the whole lot of plants examined the length of the central 

 spines ranged from 14 to 8 i mm. The length in the majority of 

 cases lay between 20 and 40 mm. Even on a single plant there 

 may be a remarkable variation in the length of the centrals. On 

 a plant of E. cocciueus the centrals, 102 in all, were measured. 

 The length varied from 12 to 40 mm. with the chief mode of the 

 curve at 24 mm. On a plant of E. conoideus it would be possible 

 to find an even greater variation in length. 



The length of the superior radials in the entire lot of plants 

 ran from 4 to 22 mm. The greatest maximum was at 8 mm. 

 The number of spines exceeding 13 mm. in length was very small. 

 In E. cocciueus the variation was from 5 to 13 mm. ; in the other 

 two species the length varied from 5 to 18 mm. 



The length of the lateral radials ranged from 8 to 35 mm., 

 with the principal modes of the curve at 18 and 21 mm. In & 

 cocciueus the lengths varied from 10 to 24 mm., with modes at 16 

 and 20 mm. ; in E. poly acanthus from 10 to 27 mm., with modes 

 at 15 and 19 mm. ; and in E. conoidcus from 1 1 to 32 mm., with 

 modes at 17, 20, and 24 mm. These lateral spines, as well as the 



