ECHINOCACTUS POI.YCEPHALUS. HEDGEHOG CACTUS. I3I 



these are early deciduous. For all nutritive purposes, the bark 

 of such a structure is sufficient to perform the functions usually 

 exercised by leaves. This also accounts for the fact that com- 

 paratively little carbon is found in Cactuses, its place being 

 generally taken by a large quantity of lime, which is drawn up 

 from the soil through the roots. 



Our Echmocactus polycephalus is one of three entirely new 

 species which were discovered by the botanists of the Whipple 

 Exploring Expedition in 1854. We quote in full the descrip- 

 tion given in the report of this expedition, as it will serve to call 

 the attention of the student to the points relied on by botanists 

 in distinguishing the various species of the genus to which this 

 Cactus belongs. Having stated that our species is found on 

 " stony and gravelly hills and in dry beds of torrents from 

 twenty miles west of the Rio Colorado to about one hundred 

 and fifty miles westward of the Mojave," and that it is "found 

 in fruit in the beginning of March," the report continues as 

 follows : " This distinguished species is simple only when quite 

 young; even the small, globose plants show several heads from 

 one base, and older cylindric stems have as many as twenty or 

 thirty heads, all pretty nearly of the same size. , . . The number 

 of the ribs varies ; in old specimens, it is generally twenty-one. 

 Areolae about half an inch in diameter and a quarter to half an 

 inch distant ixom. one another [farther apart in our illustration] ; 

 floral areolae smaller, without the ligneous glandular organs 

 noticed in others. The spines in a young, five-ribbed, living 

 specimen before us are seven radial and one central one. Very 

 soon, however, the four upper, larger spines become central and 

 four lower spines are arranged radially ; even on old and full- 

 grown specimens not more than these eight spines are found. 

 . . . Generally, however, two upper ones, weaker and less curved 

 than the two lower ones, make their appearance ; and in a few 

 instances before us, we find three to four upper radial spines, 

 the uppermost ones being quite slender. In the field, we noted 

 as many as fifteen spines occasionally, when, no doubt, seven 



