FLOWERING PLANTS AND FERNS OF ARIZONA 533 



11. MANIHOT 



Leaves long-petioled, 5- to 7-lobed; stipules small, subulate; in- 

 florescence racemose; staminate flowers several to many, at the distal 

 end of the raceme, the calyx 5-lobed, slightly inflated in bud, the 

 stamens 10, alternately long and short; pistillate flowers few to several 

 at base of the raceme, the calyx caducous, the ovary 3-celled, the 

 ovules solitary; seeds large, carunculate. 



Both of the species are rather rare in Arizona and are interesting 

 chiefly because of their kinship with M. glaziovii Muell. Arg., the tree 

 that produces the ceara rubber of commerce, and with M. utilissima 

 Pohl, from which cassava, tapioca, and other foods are derived. 



Key to the species 

 1. Primary lobes of the leaves broadly lobed toward the apex. 



1. M. CARTHAGINENSIS. 



1. Primary lobes of the leaves lobed only at or below the middle, narrow and 

 tapering to the apex 2. M. axgustiloba. 



1. Manihot carthaginensis (Jacq.) Muell. Arg. in DC, Prodr. 15 2 : 



1073. 1866. 



Jatropha carthaginensis Jacq., Stirp. Amer. 256. 1763. 



Santa Catalina and Baboquivari Mountains (Pima Count}'). 

 Southern Arizona to northern South America. 



The plant is reported to reach tree size in tropical America but is 

 much smaller in Arizona. It has been cultivated in Bahia, Brazil, for 

 the starch obtained from the fleshy roots. The oil of the seeds is both 

 emetic and cathartic, hence similar to castor oil. 



2. Manihot angustiloba (Torr.) Muell. Arg. in DC. Prodr. 15 2 : 1073. 



1866. 



Janipha manihot var. angustiloba Torr., U. S. and Mex. Bound. 

 Bot. 199. 1859. 



Xogales and in the Patagonia Mountains (Santa Cruz County), 

 Rineon, Santa Catalina, Santa Rita, and Baboquivari Mountains 

 (Pima County), 3,000 to 4,500 feet. Southern Arizona to southern 

 Mexico. 



12. STILLINGIA 



Leaves alternate to subopposite, simple, exstipulate; staminate 

 flowers borne in terminal or axillary spikes, the calyx 2-lobed, the 

 stamens 2; pistillate flowers 1 to 6 at base of the spikes, or axillary, 

 the styles 3, long, entire; seeds ovoid or ovoid-ellipsoid, small, the 

 caruncle minute or none. 



Key to the species 



1. Plant annual or perhaps sometimes perennial; leaves 3-nerved, the margins 

 with sharp teeth from base to apex, mostly elliptic-cuneate, the apex 

 attenuate 1. S. spinttlosa. 



1. Plants-perennial; leaves linear or nearly so, 1-nerved, the margins entire or with 

 a few teeth near the base or the apex but not both (2). 

 2. Low rounded leafy bush; inflorescence little overtopping the foliage; some of 

 the leaves with a few slender teeth near the base; filaments exserted 1 to 



1.7 mm. beyond the calyx at maturity 2. S. paucidbntata. 



2. Strictly erect with few, sparsely leafy stems; inflorescence generally over- 

 topping the foliage; leaves entire or rarely minutely serrulate near the 

 apex; filaments exserted 0.4 to 0.6 mm. beyond the calyx at maturity. 



3. S. LIXEARIFOLIA. 



