OF ARTS AND SCIENCES. 167 



Tradescantia leiandra, Torr. (Zebrina (?) leiandra, C. B. 

 Clarke iu A. DC Monogr. 3. 318.) At Soledad, Coahuila (2014). 

 Cells 2-seecled, or the dorsal cell 1-seeded. Referred doubtfully by 

 Clarke to Zebrina, but it has none of the characteristics of that genus, 

 and in no respect differs from Tradescantia. 700 Wright, as found 

 in Herb. Gray, includes not only this species, but a specimen of Com- 

 melina Virginica, and another of Commelina dianthifolia (as noted 

 by Mr, Clarke under that species, though it is also described by him as 

 C. leiandra). 



Tradescantia linearis, Benth. In the San Miguelito Mount- 

 ains (524: Schaffner) ; 901 Parry & Palmer, referred by Clarke to 

 T. venustula, Kunth. Collected also by Dr. Edwards at Riuconada. 

 Distinguished especially from T. venustula by the broader fleshy 

 connective. 701 Wright, referred by Dr. Torrey doubtfully to T. 

 rosea and by Mr, Clarke to this species, is distinct from both, — 

 possibly a dwarf small-flowered T. Virginica, or glabrous T. tuberosa. 



Callisia iNSiGNis, Clarke. Near Morales, San Luis Potosi (522 

 Schaffner).* 



JuNCUS Balticus, Willd, At San Luis Potosi (554 Schaffner). 



* The genera and species of the order Commelinacece in the United States, 

 studied with reference to the revision of the order by Mr. C. B. Clarke in De- 

 Candolle's MonographicR, are as follows : — 



COMMELINA, Dill. Cyme sessile within a cordate or connate bract 

 (spathe). Perfect stamens 3. Cells of the capsule 1- or 2-seeded. 



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

 1- Margins of the spathe not united. 



1. C. NUDiFLORA, Linn. (C. Cayennensis, 'Rich. C. communis, of Chapman.) 

 Slender and creeping : leaves lanceolate : spathe cordate, acute : seeds reticu- 

 lated. — From Delaware to Florida, and Missouri to Texas. 



2. C. DIANTHIFOLIA, DC. (C. linearis, Benth. C. leiandra, Clarke.) Slen- 

 der, erect, from a tuberous root : leaves linear : spathe cordate and long-atten- 

 uate : seeds wrinkled or pitted, — Northwestern Texas to New Mexico and 

 Mexico. 



M- ■*- Margins of the spathe united. 



3. C. HiRTELLA, Vahl. (C. erecta, of Gray and Chapman.) Stout, erect: 

 leaves large, lanceolate, the sheaths brown-bearded : spalhes crowded : seeds 

 smooth, — From Pennsylvania to Florida, and Kentucky to Texas. 



* * Cells I-ovuled, I-seeded : seeds smooth : roots fleshy, subtuberous. 



4. C. ERECTA, Linn. Slender, often low : leaves linear : cells all dehiscent. — 

 Pennsylvania to Florida. 



5. C. ViRGiNicA, Linn. Slender, usually tall : leaves lanceolate to linear: 

 dorsal cell indehiscent, scabrous. — From Southern New York to Michigan and 

 southward to Florida, the Indian Territory, and Mexico ; West Indies. 



