FLOWERING PLAXTS AXD FERNS OF ARIZONA 685 



to 2.5 cm. wide; anthers connivent and cohering with the large stigma. 

 The showy white flowers, opening in the evening, are said to be used 

 medicinally in Mexico. The plant is browsed by livestock (L. N. 

 Gooddutg, personal communication) but, like most plants of this 

 family, it is suspected of being poisonous. 



1. Macrosiphonia brachysiphon (Torr.) A. Grav, Svn. Fl. 2 1 :83. 



1878. 



Echites brachysiphon Torr., U. S. and Mex. Bound. Bot. 159. 



1859. 

 ? Macrosiphonia dulcis A. Xels., Amer. Jour. Bot. 21: 577. 



1934. 



Cochise, Santa Cruz, and eastern Pima Counties, 4,000 to 5.500 

 feet, dry mesas and slopes, August and September, type of M. dulcis 

 (not seen by the writers), from the Huachuca Mountains (Goodding 

 2413). Southern Xew Mexico and Arizona, northern Mexico. 



4. APOCYXUM. » Dogbane, ixdiax-hemp 



Plants herbaceous; stems leafy, commonly erect; leaves large, oppo- 

 site (exceptionally in whorls of 3) ; flowers small for the family, in 

 usually dichotomous compound cymes; corolla cylindric, urceolate, or 

 campanulate,pink or whitish, the tube with internal basal appendages; 

 anthers connivent and coherent with the stigma; follicles long, 

 slender, terete. 



The American aborigines used the bark of Apocynum for cordage. 

 A cardiac stimulant similar, although inferior, to digitalin has been 

 obtained from the root of A. cannabinum. The medicinal properties 

 of the plant appear to have been known to the Indians. Some, if not 

 all, of the species develop cyanogen and are toxic to cattle, horses, 

 and sheep in both the green and the dry state. 



Key to the species 



1. Corolla whitish or greenish, cylindric or narrowly urceolate, seldom more than 

 3 mm. long, not more (usually less) than twice as long as the calyx, the 

 lobes erect or nearly so; leaves ascending or somewhat spreading, slightly 

 paler beneath (2) . 

 2. Calyx lobes less than 2 mm. long; corolla cylindric; plant glabrous through- 

 out; leaves mostly short-petioled, the blades narrowed at base. 



1. A. SUKSDORFII. 



2. Calyx lobes 2 mm. long or longer (3). 



3. Leaves of the main stem distinctly petioled, the blades narrowed at base, 

 oblong-lanceolate to ovate; plant pubescent or glabrous. 



2. A. CAXXABIXUM. 



3. Leaves of the main stem sessile or subsessile, the blades rounded or sub- 

 cordate at base, lanceolate or oblong-lanceolate; plant glabrous 

 throughout .__ 3. A. sibiricum. 



1. Corolla normally pink or striped with pink, campanulate or broadly urceolate, 

 usually at least 4 mm. long, 2 to 3 times as long as the calyx, the lobes 

 more or less spreading; leaves wide-spreading or drooping, the blades 

 commonly ovate or oblong-ovate, deep green above, conspicuously paler 

 or whitish beneath (4). 

 4. Calyx usually about one-third as long as the corolla; corolla 5 mm. long or 

 longer, broadly campanulate, the lobes conspicuously spreading, often 



recurved at apex 4. A. axdrosaemifolium. 



4. Calyx about half as long as the corolla; corolla 4 to 5 mm. long, narrowly 

 campanulate or urceolate, the lobes moderately or slightly spreading, not 

 recurved 5. A. medium. 



Reference: Woodson, Robert E. Je. stvdies in the ai-ocynaceae I. Mo. Bot. Gard. Ann. 

 17: 83-212. 1930. 



