XYRIDACEAE 231 



PONTEDERIACEAE and BROMELIACEAE). Gynoecium compound, superior or 

 rarely inferior. Fruit a capsule or utricle, or baccate. Seed with mealy endo- 

 sperm. 



Ovary 1-celled, with parietal placentae: inflorescence without a spathe. 



Caulescent moss-like herbs : flowers axillary to leaf-like bracts : sepals alike : styles wholly united. 



Fam. 1. MAYACACEAE. 

 Acaulescent rush-like herbs : flowers in terminal dense spikes : sepals of 



2 forms, or 1 sepal wanting : styles partially united. Fam. 2. XYRIDACEAE. 



Ovary 2-3-celled, if incompletely so or if nearly 1-celled then the flowers 



in'. a spathe. 

 Flowers minute, monoecious or dioecious, in dense heads each seated in 



an imbricated involucre. Fam. 3. ERIOCAULACEAE. 



Flowers conspicuous or relatively so, perfect. 



Terrestrial or aquatic plants : foliage not scurfy : stigmas united. 



Calyx and corolla free, of very different members : stamens free. Fam. 4. COMMELINACEAE. 

 Calyx and corolla of quite similar members and partially united : 



stamens partially adnate to the perianth. Fam. 5. PONTEDERIACEAE. 



Epiphytes (our species), with scurfy foliage : stigmas 3. Fam. 6. BROMELIACEAE. 



FAMILY 1. MAYACACEAE Walp. MAYACA FAMILY. 



Perennial caulescent moss-like marsh herbs. Leaves numerous : blades nar- 

 row, pellucid, flaccid, 1 -nerved, entire below the notched apex. Flowers per- 

 fect, borne on axillary pedicels. Perianth regular, persistent. Sepals narrowed 

 upward. Petals 3, white or purple, broadened upward. Androecium of 3 hy- 

 pogynous stamens. Filaments filiform. Gynoecium 3-carpellary. Ovary 1-celled 

 with 3 parietal placentae. Style filiform. Ovules orthrotopous. Capsule 3- 

 celled : valves 3, with the placentae at the middle. Seeds rounded. Testa fur- 

 rowed and pitted. Embryo at the top of the mealy endosperm. 



1. MAYACA Aubl. 

 Characters of the family. The plants flower mainly from spring to fall. 



Pedicels much longer than the leaves : capsule globular or ovoid. 1. M. Aubletii. 



Pedicels shorter than the leaves : capsule oblong. 2. M. fluviatilis. 



1. Mayaca Aubl6til Michx. Stems tufted or matted, 2-20 cm. long : leaves approx- 

 imate or densely crowded ; blades narrowly lanceolate or almost linear, 3-5 mm. long, 

 sharply notched at the apex : pedicels 8-20 mm. long, surpassing the leaves : sepals about 

 4 mm. long at maturity : capsules globular or ovoid, 4-4.5 mm. long. \_M. Miclmuxii 

 Schott&Endl.] 



In springy places or on the margins of pools or streams, Virginia to Florida and Texas. 



2. Mayaca fluviatilis Aubl. Larger than M. Aubletii, the stems often 40 cm. long : 

 leaves very numerous, approximate ; blades narrowly linear-lanceolate to linear-filiform, 

 4-12 mm. long, very flaccid: pedicels 2-5 mm. long, shorter than the leaves : sepals 3-4 

 mm. long : capsules oblong, 4-5 mm. long. 



In ponds, pools and streams, Georgia and Florida to Mississippi. Also in tropical America. 



FAMILY 2. XYRIDACEAE Lindl. YELLOW-EYED GRASS FAMILY. 



Annual or perennial scapose herbs. Leaves basal, mostly 2-ranked, sword- 

 like. Scapes simple, terete or variously angled, or winged. Flowers perfect, 

 subtended by crustaceous closely imbricated bracts, forming a compact terminal 

 spike. Sepals 3, the two lateral firm, keeled and often appendaged, persistent, 

 the third deciduous (or wanting). Corolla white or yellow, regular or nearly so. 

 Petals 3, fugacious : blades spreading. Androecium of 3 stamens. Filaments 

 usually alternating with 3 staminodia. Gynoecium 3-carpellary. Ovary 1-celled, 

 sometimes incompletely 3-celled, with 3 parietal placentae. Ovules numerous, 

 orthotropous. Style unappendaged at the base (or appendaged). Stigmas 3. 

 Fruit a 3-valved capsule. Seeds numerous. 



1. XYRIS L. 



Characters of the family, omitting those in parentheses. YELLOW-EYED GRASS. 



A. Annual or biennial plants : leaves mainly shorter than the sheath of the scape. 



Keel of the lateral sepals smooth or erose-scabrous. 1. X. brevifolia. 



Keel of the lateral sepals ciliate-f ringed. 2. X. flabeUiformis. 



