34 TRANS. ST. LOUIS ACAD. SCIENCE. 



^ westwardly into the mountain region ; T. rupicola inhabits the 

 southern portion of the plains. Clistoyucca and Hesperoyucca 

 are southwestern types, peculiar to Arizona and California. 



SYSTEMATIC ARRANGEMENT. 



In the foregoing pages it has been shown that in the fruit and 

 seed we have excellent characters for the arrangement of the 

 species of Yucca into several very natural groups ; the nature of 

 the edge of the leaves furnishes proper subdivisions ; the specific 

 characters are based upon the differences of trunk, leaves, flowers^ 

 and also of fruit and seed. 



Yucca, Lin. 



Perigonium patulum demum globoso-campanulatum six-parti- 

 tum subpersistens ; segmenta lanceolato-ovata acutiuscula ; fila- 

 menta clavata multo breviora, antherae biloculares introrsum 

 dehiscentes parvag ; pollen globosum ; ovarium tricarpellare tri- 

 loculare, loculi incomplete bilocellati : stigmata 3 emarginata 

 plus minus connata tubum stigmaticum eflbrmantia ; ovula plu- 

 rima compressa horizontalia anatropa brevissime funiculata 6- 

 seriata ; fructus baccatus seu capsularis incomplete 6-locularis ; 

 semina obovato-triangularia compressa horizontalia 6-seriata 

 nigra, embryo diagonalis albumini corneo aequilongus. 



Plantas in America tropica cis aequatorem et praecipue in 

 boreali calidiore indigenae ; caudice arborescente elatiore vel 

 humiliore, saepe hypogaeo ; foliis in apice caudicis confertis 

 lineari-lanceolatis crassis rigidis rarius flaccidis apice plerumque 

 spinescentibus ; panicula terminali multiflora subsessili vel in 

 scapo bracteato elata ; floribus majoribus albidis. 



I. EuYUCCA : filamenta clavata obtusa papillosa pistillo plerumque 

 breviora demum patula vel recurva, antherae cordato-sagittatae; 

 ovarium prismaticum, stigmata papillosa. 



A. Sarcoyucca : fructus indehiscens baccatus pendulus; semina 

 crassa undulata immarginata albumine lobato-ruminato. 

 Plantae plerumque arborescentes panicula saepius sessili. 



* Folia margine serrulato-asperata. 



I. Yucca aloifoua, Lin.: caule elatiore; foliis lineari- 

 lanceolatis supra leviter concavisnunc rigidis pungentibus Isevibus 

 margine asperrimis ; bracteis paniculae subsessilis ovatae vel 

 oblongae glaberrimas minoribus triangularibus marcescentibus ; 



