222 THE PLANT WORLD 



whitish flowers each remain open but a short time and ap- 

 parently are pollinated by insects. A succession of them 

 ensues, and although practically finished during May or 

 June, yet belated buds open at various times, one havin^r 

 been seen as late as the middle of November. The seedy 

 fruits mature in great quantity in midsummer, and are much 

 prized by the Papagoes, who make much use of them in 

 various ways. 



The prickly pears, or opuntias with flat stems, begin to 

 make some growth of new joints and to push out flower buds 

 in March, and late In that month or early in April bloom 

 in great profusion, the fruits maturing early and dropping to 

 the ground. Fifteen or twenty species are native to the 

 Tucson region, but the greatest confusion pre\'ails as to their 

 identity. Of the various desert plants, this group has been 

 the subject of the most inquirv as to its possible economic 

 utilization. After a consideration of the various practical 

 questions connected with open cattle ranges, it has been found 

 that the best use of them for forage is made by growing, 

 or allowing to grow, spinose species, from which the spines 

 are burned when they are to be consumed by animals. This 

 is now done in the open range. Unarmed forms are subject 

 to the attacks of so many animals that it is difl'icult to bring 

 them to any material growth. A few species are known in 

 which the spines are very sparse. One of these Opunt'ui 

 laevis occurs in the canyons of the Santa Catalina, Santa 

 Rita and Tortolita Mountains chiefly upon rocks or in 

 places inaccessible to grazing animals. 



OpiiHtid chlorotha also has a \ery few spines, but the 

 circular fronds are furnished with dense bundles of minute 

 spicules or glochids. The highly coloreci reddish joints 

 and the delicately tinteci flowers make this a \-erv attractive 

 plant and it may be found in some of the gardens of Tucson. 

 A half dozen other species are abundant on the mesa-like 

 plains and slopes, two being encountered at elevations as high 

 as 7000 feet In the Santa Catalina mountains. 



