62 LEMNACEAE. 



Lemna trisulca L., of the cooler parts of the north temperate zone, is 

 recorded as Bermudian by Eein and copied by Hemsley, but it has not been 

 found by recent collectors, and probably could not withstand the warm climate. 

 The plant described under that name by H. B. Small is Salvinia Olfersiana. 



Order 8. XYRIDALES. 



Monocotyledonous herbs, mostly with narrow leaves. Flowers usually 

 complete, their parts mostly in 3's or 6's. Corolla re^ilar or nearly so 

 (except in Commelina). Ovary compound, superior. Endosperm of the 

 seed mealy. 



Plants not epiphytic ; leaves not scurfy. 



Perianth of 2 series of parts, the outer (sepals) green, the inner (petals) colored. 



Fam. 1. COMMELINACEAE. 



Perianth G-parted. Fam. 2. Pontederiaceae. 



Plants epiphytic ; leaves scurfy. Fam. 3. Bromeliaceae. 



Family 1. COMMELINACEAE Reichenb. 



Spiderwort Family. 



Perennial or annual leafy herbs with regular or irregular perfect and 

 often showy flowers in cymes, commonly subtended by spathe-like or leafy 

 bracts. Perianth of 2 series; a calyx of mostly 3 persistent sepals and a 

 corolla of mostly 3 membranous and deciduous or fugacious petals. Sta- 

 mens mostly 6, hypogynous, rarely fewer, all similar and perfect or 2 or 3 

 of them different from the others and sterile; filaments filiform or some- 

 what flattened; anthers 2-celled, mostly longitudinally dehiscent. Ovary 

 superior, sessile or xery nearly so, 2-3-celled ; ovules 1 or several in each cell, 

 anatropous or half anatropous; style simple; stigmas terminal, entire or 

 obscurely 2-3-lobed. Seeds solitaiy or several in each cell of the capsule. 

 Capsule 2-3-celled, loculicidally 2-3-valved. Embryo small. Endosperm 

 copious. About 25 genera and 350 species, mostly natives of tropical 

 regions, a few in the temperate zones. 



Fertile stamens 2 or 3. 1. Commelina. 



Fertile stamens 6. 2. ZehHna. 



1. COMMELINA L. 



Somewhat succulent, branching herbs, with short-pet ioled or sessile leaves, 

 and irregular mostly blue flowers in sessile cymes subtended by spathe-like 

 bracts. Sepals unequal, the larger ones sometimes slightly united. Petals 

 unequal, 2 of them larger than the third. Perfect stamens 3, rarely 2, one of 

 them incurved and its anther commonly larger. Sterile stamens usually 3, 

 smaller, their anthers various. Filaments all glabrous. Capsule 3-celled. 

 Seeds 1 or 2 in each cavity, the testa roughened, smooth or reticulated. [Dedi- 

 cated to Kaspar Commelin, 1667-1731, Dutch botanist.] About 95 species of 

 wide distribution in warm and temperate regions. Type species: Commelina 

 communis L. 



Spathes not united, acuminate. 1. O. longicaulis. 



Spathes united toward the base, acute. 2. C. elegans. 



