a globose to cylindrical headlike spike of perfect trimerous flowers; floral bracts 

 usually densely spirally imbricate, coriaceous or rigid, typically concave and 

 dorsally marked with a blotch of different color or texture, the upper bracts sub- 

 tending a solitary flower, the lower ones often sterile and forming an involucre; 

 calyx irregular, glumaceous. the 2 persistent lateral sepals cymbiform and dorsally 

 keeled or winged, the larger anterior sepal obovate and enfolding the corolla in 

 bud and deciduous with it; petals yellow or rarely whitish, obovate, with claws 

 that are more or less coherent, fugacious; stamens inserted on the petal claws, the 

 basifixed anthers extrorse; staminodes (when present) alternate with the petals, 

 bifid and bearded at apex; style 3-cleft; capsule ellipsoid, free, 1 -celled, with 3 

 parietal somewhat projecting placentae, 3-valved, with numerous more or less 

 ribbed ellipsoid to fusiform orthotropous seeds. 

 A family of two genera, mostly in tropical regions. 



1. Xyris L. Yellow-eyed Grass 



Characters of the family. A genus of about 250 species distributed mostly in 

 tropical and subtropical regions in America, Africa and Australia. 



1. Keel of lateral sepals ciliate or fimbriate (2) 



1. Keel of lateral sepals lacerate, usually quite thin, rarely entire (4) 



2(1). Tips of lateral sepals exserted beyond the subtending bract, fimbriate 

 (usually crisped); spikes seldom shorter than 1 cm.; seeds seldom 

 shorter than 0.8 mm., fusiform, with broad flat longitudinal ridges; 

 sheaths of the scape exceeded by the leaves 3. X. caroliniana. 



2. Tips of lateral sepals not exserted beyond the subtending bract and not fim- 



briate (in old or dried spikes the lateral sepals may separate from 

 the bracts and appear to be exserted but exsertion is supposed to 

 mean that bracts are shorter than sepals); seed lengths and shapes 

 various but the seeds without broad flat longitudinal ridges; sheath 

 lengths various (3) 



3(2). Leaves ascending, twisted, strongly grooved; spikes ovoid, the bracts and 

 lateral sepals with a small apical tuft of short reddish-brown hairs; 

 bases of leaves abruptly expanded, pinkish or purplish, becoming 

 dark-brown, the bases of the plants therefore bulbous and the 

 outermost leaves often scalelike 5. X. torta. 



3. Leaves spreading, scarcely twisted; spikes lance-ovoid to ellipsoidal; bracts 



and sepals not as above; bases of leaves longitudinally striate (the 

 innermost fresh leaf bases white, the striae in dark contrast) and 

 with the bases of the plants often invested by a stubble or ramentum 

 of fibrous dead leaf bases 2. X. ainhisua. 



4(1). Leaves filiform or rarely somewhat linear, the blades gradually expanding 

 below into lustrous rich-brown or tan hard bases; plants densely 



cespitose; spikes ovoid and seldom longer than 1 cm 



\. X. Baldwiniana. 



4. Leaves broader or not as above, the bases softer or of a different color; plants 



or spikes not as above (5) 



5(4). Bases of the leaves rather abruptly expanded into thickened flaring equi- 

 tant zones, thus the plant bulbous-based (the outer leaves are often 

 shorter, darker and scalelike); scapes often flexuous, usually quite 

 twisted, the green upper portion of leaf blades often conspicuously 

 twisted; flowers opening in the afternoon 4. X. platylepis. 



5. Bases of the leaves and the plant bases not as above; scapes usually not flexu- 



ous, the blades not conspicuously twisted; flowers opening in the 

 early or late morning (6) 



580 



