A DESERT GRAVEYARD 183 



ers are quite narrow, a little less than three inches in length, 

 and covered with a dense layer of cream-yellow hairs. These 

 great plants grow singly on the highlands of San Luis Potosi, 

 Central Mexico, and often attain an age of a thousand years 

 and a weight of over five thousand pounds. 



How to grow 



This rare cactus grows very slowly. It thrives In sandy 

 or gravelly clay loam with sunny exposures, and with occa- 

 sional irrigation to moisten the soil during dry periods and 

 during the growing season. The plants will grow out of 

 doors or indoors and are not injured by a temperature twenty- 

 five degrees below freezing; from zero weather they should 

 be given protection. 



Whipple's Visnagita (Echinocactus Whipple! — 



Sclerocactus Whipplei) 



(Named in honor of Lieutenant A. W. Whipple, In charge 



of the Whipple Expedition in 1853-1854, when this plant 



was discovered) 



How to identify and how it grows 



This little cactus grows only three to six Inches tall, and 

 about the same in diameter, singly or occasionally in clumps. 

 It is generally to be seen growing in the protection of shrubs 

 at about ^wt thousand feet. The stem Is lined with thirteen 

 to fifteen prominent splraled ribs, and seven to eleven white 

 radial spines. There are also four black and white central 

 thorns which turn red and finally ash-colored, and the lowest 

 of these spines is sharply hooked. The flowers cluster at the 

 top of the plant, bell-shaped blossoms purplish or rose- 

 tinged, with a reddish style hairy its full length. The red- 

 dish fruit Is oblong and has colorless scales, each of which 

 bears a tuft of hairs In the axil. 



