(J6 MISSOURI BOTANICAL GARDEN. 



South of Torreon, along the Mexican Central railroad, 

 particularly from about Picardias to about Jalisco, this 

 small tree is abundant, on or near the rocky hillsides, and 

 conspicuously contrasted with accompanying Y. Treculeana 

 bv its very glaucous narrower foliage. It may be that small 

 trees between Monterey and Saltillo, visible from the Mexi- 

 can National railroad, extend its range to the east. 



Yucca rigida, the specific name of which is descriptive 

 only when its dried leaves are compared with those of Y. 

 i-upicola, is one of the handsomest tree Yuccas, in its foli- 

 age. The slender trunks are commonly simple, but occas- 

 ionally once or more forked, with elongate branches. When 

 well developed the leaves are from .3 to .6 m. long, 20 to 30 

 mm. wide, and, as would scarcely be inferred from herba- 

 rium material, decidedly concave up to the very slender 

 pungent terete point ; both surfaces are closely ridged and 

 often minutely roughened, and the bright yellow margin, 

 though occasionally nearly smooth, is usually finely den- 

 ticulate, so as to possess a keen cutting power. Though, as 

 has been said, the plant forms a low tree when developed, 

 a few specimens have been seen bearing panicles when still 

 practically acaulescent, as is also true of Y. radiosa about 

 El Paso. The panicles are loosely branched shortly above 

 the crown of leaves, and the very hard oblong capsules, 

 about 50 mm. long and 25 mm. in diameter, are parted 

 about to the middle into 3 valves which are conspicuously 

 flattened or even concave on the back, and with short out- 

 curved apical points, and the inner or placental dehiscence 

 is very narrow, so that the small thin black seeds escape 

 only when jarred out edgewise. 



Dr. Engeimann would doubtless have given specific rank 

 to this tree, had he not misapprehended its relation in size 

 and field appearance to the typical acaulescent often twisted- 

 leaved Y. rupicola, which, in contrast with it, he called 

 variety tortifolia. The foliage and capsular characters 

 added above leave no room for question as to its specific 

 distinctness from the latter. 



