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THE NATIONAL GEOGRAPHIC MAGAZINE 



THE PIvANT THAT OWNS A CISTERN 



Probably the most extraordinary prod- 

 uct of the Sonora Desert, west of Torres, 

 Mexico, is the guarequi (IberviUea 

 sonorcp), a tendril-bearing plant whose 

 inordinately thickened root and stem 

 base lies gray and half exposed upon the 

 ground beneath some trellising shrub (see 

 page 696). These tuberous formations 

 may be seen during the dry season lying 

 about wholly unanchored, as the slender 

 roots dry up with the close of the vege- 

 tative season, which lasts but a few 

 weeks. 



In February, 1902, some of these 

 tubers were taken to the New York Bo- 

 tanical Garden, and a large specimen not 

 treated in any way was placed in a mu- 

 seum case, where it has since remained. 

 Annually, at a time fairly coincident with 

 the natural vegetative season in its na- 

 tive habitat, the major vegetative points 

 awaken and send up a few thin shoots 

 which reach a length of about 2 feet only, 

 since they do not obtain sunlight. After 

 a period of a few weeks, they die down 

 again and the material in them retreats 

 to the tuber to await another season. 

 Seven periods of activity have thus been 

 displayed by this specimen with no ap- 

 parent change in its structure or size. It 

 does not seem unreasonable to suppose, 

 therefore, that the guarequi is a storage 

 structure of such great efficiency that 

 water and other material sufficient to 

 meet the needs of the plant for a quarter 

 of a century are held in reserve in its 

 reservoirs. 



The guarequi is reputed locally to be 

 very poisonous, but repeated tests by Dr 

 William J. Gies and Miss Julia Emerson, 

 with living material, hot and cold water 

 extracts, and alcoholic extracts, fail to 

 produce any results with the various ani- 

 mals used as test objects. It is quite pos- 

 sible, however, that the living vines or 

 the fruits might yield substances upon 

 which the prevailing opinion is based. 



The morning-glory {Ipomoca arbores- 

 cens) is here a tree 20 to 30 feet high, 

 with smooth chalky gray trunk and 

 branches. During February it is leafless 

 throughout, while its large white flowers 



open one by one on the ends of the naked 

 branches. From its white bark the tree 

 is sometimes known as palo bianco, and 

 from the gum or resin, -which exudes 

 from incisions made in it for the purpose 

 and which is used as incense in religious 

 ceremonies, it is called also palo santo. 



WONDEREUI. CACTI THAT STORE HUNDREDS 

 OE GAEEONS OE WATER 



One of the striking features of the 

 Tehuacan Desert of southern Mexico is 

 the extreme localization, or strictness of 

 colonization, exhibited by many species 

 which are found to cover an area of a 

 few square yards, the face of a slope, the 

 crest of a cliff, or the floor of a barranca, 

 with no outliers and with the nearest 

 colony perhaps many miles away. 



The Cactacese are more abundant here 

 than in any other part of the world yet 

 visited, several of the species being mas- 

 sive forms, which constitute very promi- 

 nent features of the landscape. 



Cephaloc evens iiiacrocephalus (see 

 page 698) is a tall species of the massive- 

 ness of the saguaro, and like it having 

 a central shaft bearing numbers of 

 branches which are more closely ap- 

 pressed. It was seen only along the cliff 

 near the Rancho San Diego, along the 

 eastern edge of the valley. Pilocereus 

 fiilviceps (see page 699), of more gen- 

 eral distribution on slopes, has a series of 

 branches, in many instances 40 or 50 in 

 number, densely clustered and arising 

 from a short trunk, which barely rises 

 from the ground before it branches. 



Bchinocactus was represented by a half 

 dozen species, of which one, B. grand e 

 (see page 701), is undoubtedly the most 

 massive of all the genus, being as much 

 as 8 or 9 feet in height and 30, or even 

 36, inches in thickness, which, with the 

 many convolutions of its surface, makes 

 it a very grotesque feature of the scenery. 

 The young of this species are character- 

 ized by very striking cross-stripes which 

 disappear with age. Upon testing the 

 pith to compare the watery content with 

 the northern species, it was found that 

 so much calcium had been taken up and 

 stored in the form of calcium oxalate or 



