RUBIACEAE. 86l 



free from the calyx, globose-didymous, or emarginate at the apex, loculicidally 

 dehiscent above. Seeds peltate, concave, not angled. Seed-coat reticulate or 

 roughened; endosperm horny; embryo club-shaped. [Named in honor of Dr. 

 William Houston, botanist and collector in South America, died 1733. J About 25 

 species, of N. Am. and Mex. 



* Plants 2.5-18 cm. high; peduncles i-flowered. 

 Peduncles filiform, 2.5-6 cm. long. 



Erect; leaves obovate or spatulate, narrowed into petioles. 1. //. coerulea. 



Diffuse or spreading ; leaves nearly orbicular. 2. H. serpyllifolia. 



Peduncles 0.6-3.5 cm. long, stouter. 



Calyx-lobes narrow, about equalling the capsule. 3. H. minor. 



Calyx-lobes broad, much exceeding the capsule. 4. H. minima. 



** Plants 10-45 cm - high; flowers cymose. 

 Calyx-lobes lanceolate-subulate, 2 to 3 times as long as the capsule. 5. H. lanccolata. 

 Calyx-lobes linear-subulate, scarcely longer than the capsule. 



Leaves broad, ovate, ovate-lanceolate, or lanceolate. 6. H purpurea. 



Leaves oblong or spatulate, ciliate. 7. H. ciliolata. 



Leaves linear-lanceolate or oblanceolate, not ciliate. 8. H. longifolia. 



Leaves filiform or narrowly linear. 



Flowers loosely cymose on filiform pedicels ; leaves not fascicled. 



9. H. tenui/olia. 

 Flowers densely cymose on very short pedicels ; leaves usually fascicled. 



10. H. angustifolia. 



i. Houstonia coerulea L. Bluets. Innocence. (I. F. f. 3393.) Erect, 

 7-18 cm. high, glabrous, or nearly so, perennial by slender rootstocks, forming 

 dense tufts. Lower and basal leaves spatulate or oblanceolate, about 12 mm. long, 

 sometimes hirsute or ciliate, narrowed into a petiole, the upper oblong, sessile; 

 flowers solitary on filiform peduncles; corolla salverform, violet, blue, or white, with 

 a yellow center, 8-12 mm. broad, its tube slender and about the length of the lobes; 

 capsule didymous, compressed, about 4 mm. broad, broader than long, the upper 

 half free from the calyx and shorter than its lobes. In open grassy places, or on 

 wet rocks, N. S. to Quebec, Mich., Ga. and Ala. April-July, or producing a few 

 flowers through the summer. 



2. Houstonia serpyllifolia Michx. Thyme-leaved Bluets. (I. F. f. 

 3394.) Perennial; stems prostrate or diffuse, slender, glabrous, 1-2.5 dm. long. 

 Leaves orbicular or broadly oval, abruptly petioled, 6-8 mm. long, sometimes hi- 

 spidulous, or those of the flowering stems narrower, distant ; corolla usually deep 

 blue, 8-12 mm. broad, its tube rather shorter than the lobes; capsule similar to that 

 of the preceding, but usually slightly larger, nearly as long as the calyx. Moun- 

 tains of Penn., Va. and W. Va. to S. Car. and Tenn. May. 



3. Houstonia minor (Michx.) Britton. Small Bluets. (I. F. f. 3395.) 

 Annual, glabrous or nearly so, branched from the base, 2-15 cm. high. Lowerand 

 basal leaves oval or ovate, 10-12 mm. long, narrowed into petioles, the upper nar- 

 rower and sessile; corolla violet-blue or purple, 6-8 mm. broad, its tube about equal- 

 ling the lobes; capsule compressed, didymous, 5-6 mm. broad, its upper part free 

 from the calyx. In dry soil, Va. to Fla., Ark. and Tex. March-April. 



4. Houstonia minima Beck. Least Bluets. (I. F. f. 3396.) Annual, 

 spreading or diffuse, 2.5-6.5 cm. high, roughish. Lower and basal leaves oval or 

 ovate, the upper oblong, sessile; flowers 8-10 mm. broad; corolla violet or purple, 

 the tube longer than the lobes; capsule didymous, compressed, about 6 mm. broad, 

 its upper part free from the calyx. In dry soil, Mo. and 111. to Kans., Ark. and 

 Tex. March-April. 



5. Houstonia lanceolata (Poir.) Britten. Calycose Houstonia. Gla- 

 brous, or pubescent, perennial, 1.5-3 dm - ni g h - Leaves lanceolate to linear-lanceo- 

 late, sessile or the lowest spatulate and narrowed into petioles. Corolla little ex- 

 ceeding the calyx; capsule about 3 mm. in diameter, much shorter than the lanceo- 

 late rigid calyx-lobes. N. C. to Ala., Ky., Tenn. and Mo. May-June. [//. pur- 

 purea calycosa A. Gray.] 



6. Houstonia purpurea L. Large Houstonia. (I. F. f. 3397.) Peren- 

 nial, tufted, glabrous or somewhat pubescent, 1-4.5 dm. high. Leaves sessile, or 

 the lower ones short-petioled. 3-5-nerved. 1-5 cm. long, the margins often ciliate; 

 pedicels 2-8 mm. long; corolla purple or lilac, funnelform, 6-8 mm. long, the tube 



