SPIDERWORT FAMILY. 453 



branching stems beset with linear, pellucid, sessile leaves ; the flower with 

 a slender, pale yellow perianth, of 6 narrow, equal divisions raised to the 

 surface on a very slender tube. 



CXXI. commelinacej:, spiderwort family. 



Herbs with mucilaginous juice, jointed and mostly branch- 

 ing leafy stems, and perfect sometimes irregular flowers, hav- 

 ing a perianth of usually 3 green and persistent sepals, and 3 

 ephemeral petals (these commonly melt into jelly the night 

 after expansion) ; 6 stamens, some of them often imperfect, 

 and a free 2-3-celled ovary ; style and stigma one. Pod 2-3- 

 celled, few-seeded. Leaves ovate to linear, flat, sheathing at 

 the base. Not aquatic, the greater part tropical. 



* Perfect stamens 8, the other 3 with sterile cross-shaped anthers. 



1. COMMELINA. Flowers blue, irregular. Sepals unequal, 2 of them sometimes united 



by their contiguous margins. Two of the petals rounded and on slender claws, the 

 odd one smaller or abortive. Filaments naked. Leaves abruptly contracted and 

 sheathing at base, the uppermost forming a spathe for the flowers. 



* * Stamens all & perfect, or- rarely 1 imperfect. 



2. TRADESCANTIA. Flowers regular. Petals all alike and distinct, ovate, sessile. Sta- 



mens with bearded filaments. Ovary 2-3-celled, the cells 2-ovuled. Erect herbs with 

 flowers in axillary and terminal umbellate clusters or heads (Lessons, Fig. 880). 

 8. ZEBRINA. Flowers irregular. Calyx tubular below, either equally 3-parted, or 2-parted 

 above and a broader lobe below. Corolla with a slender tube longer than the calyx, 

 the lobes ovate and spreading, subequal. Filaments nude or bearded. Ovary 8-celled, 

 each cell 1-2-ovuled. Trailing or scandent herbs, with flowers mostly in 2's. 



1. COMMELINA, DAY FLOWER. (J. & G. Commelin, early Dutch 

 ' botanical authors. A third brother published nothing. In naming this 

 genus for them, Linnaeus is understood to have designated the two 

 former by the full-developed petals, the latter by the smaller or abortive 

 petal.) Ours are branching perennials, or continued by rooting from 

 the joints ; in alluvial or moist shady soil ; flowers all summer. 



* Cells 1-seeded ; seeds smooth. 



C. ere'cta, Linn. Stem slender and low ; leaves linjar ; cells all dehis- 

 cent. Penn., S. 



C. Virgfnica, Linn. S. N. Y., S. and W.; stems reclining and root- 

 ing at base ; leaves oblong-lanceolate or narrower ; spathes scattered, 

 conduplicate, round-heart-shaped when laid open ; odd petal inconspicu- 

 ous ; dorsal cell indehiscent, scabrous. 



* * Ventral cells usually 2-seeded (2-ovuled), and the dorsal one 1-seeded. 



C. nudifldra, Linn. Slender and creeping, glabrous ; leaves small and 

 lanceolate ; margins of the cordate-ovate spathe not united ; seeds reticu- 

 lated. Del. to Ind., and S. 



C. hirte'lla, Vahl. Stem erect (2°-4°) and stout ; leaves larger, lance- 

 olate, the sheaths brown- bearded ; margins of the spathe united ; seeds 

 smooth. Penn., W. and S. 



