LABIA TAE. 805 



[Name used by Thcophrastus; from the nymph Minthe.] About 30 species, of the 

 north temperate zone. 



* Whorls of flowers in terminal spikes, or some in the upper axils. 

 Plants glabrous or very nearly so. 



Spikes slim, narrow, mostly interrupted ; leaves sessile, or nearly so. 



1. M, s pic at a t 

 Spikes thick, mostly dense, at first short; leaves petioled. 



Leaves lanceolate or oblong, acute. 2. M. piperita. 



Leaves ovate, obtuse, or the upper acute, subcordate. 3. M. citrata. 



Plants villous, hirsute or canescent, at least at the nodes. 

 Spikes slim or narrow, often interrupted. 



Leaves lanceolate or ovate-lanceolate, acute. 4. M. longifolia. 



Leaves elliptic or ovate-oblong, obtuse, reticulated beneath. 



5. M. rotundi/olia. 

 Spikes 10-12 mm. thick, dense, elongated or short. 



Leaves sessile ; spikes 2-8 cm. long; plant canescent. 6. M. alopecuroides. 



Leaves distinctly petioled, or the uppermost sessile ; spikes short. 



Leaves simply serrate. 7. M. aquatica. 



Leaves mostly incised, the margins crisped and wavy. 8. M. crispa, 

 * * Whorls of flowers all axillary. 

 Leaves crenate-dentate ; calyx-teeth triangular, short. 9. M. arvensis. 



Leaves sharply serrate ; calyx-teeth subulate. 



Calyx-teeth ciliate, the tube glabrous; leaves ovate. 10. M. gentilis. 



Calyx densely or sparsely pubescent all over. 



Leaves ovate, pubescent on both sides; hairs of the stem reflexed. 



11. M. sativa. 

 Leaves oblong or ovate-oblong, nearly or quite glabrous. 12. M. Canadensis. 



1. Mentha spicata L. Spearmint. (I. F. f. 3174.) Perennial by leafy 

 stolons ; stem erect, 3-5 dm. high. Leaves lanceolate, sessile or short-petioled, 

 sharply serrate, acute or acuminate, the largest about 7 cm. long ; whorls of flow- 

 ers in spikes which become 5-10 cm. long in fruit, the one terminating the stem 

 surpassing the lateral ones ; bracts subulate-lanceolate, ciliate; calyx campanulate, 

 its teeth subulate, nearly as long as the tube ; corolla glabrous. In moist fields or 

 waste places, N. S. to Ont., Minn., Utah, Fla. and Kans. Nat. from Europe. 

 July -Sept. 



2. Mentha piperita L. Peppermint. (I. F. f. 3175.) Perennial by subter- 

 ranean suckers, 3-9, dm. high. Leaves lanceolate, petioled, dark green, acute, 

 sharply serrate, glabrous on both sides, or pubescent on the veins beneath, the 

 larger 3-8 cm. long ; whorls of flowers in spikes, which are obtuse, and become 

 2-8 cm. long in fruit, the middle one at length overtopped by the lateral ones ; 

 bracts lanceolate, acuminate ; calyx tubular- campanulate, glabrous below, its teeth 

 subulate, usually ciliate, one-half as long as the tube or more ; corolla glabrous. 

 In wet soil, N. S. to Minn., Fla. and Tenn. Nat. from Europe. July-Sept. 



3. Mentha citrata Ehrh. Bergamot Mint. (I. F. f. 3176./ Perennial 

 by leafy stolons ; stem weak, decumbent or ascending, 3-6 dm. long. Leaves 

 petioled, thin, ovate or ovate-orbicular, obtuse or the upper acute at the apex, 

 sharply serrate, the larger about 5 cm. long ; whorls of flowers in terminal short 

 obtuse spikes, and commonly also in the uppermost axils ; calyx glabrous, its teeth 

 subulate, one-half as long as the tube, or longer ; corolla glabrous. In wet soil, 

 Staten Island. N. V. and Ohio. Adventive from Europe. July-Sept. 



4. Mentha longifolia (L.) Huds. Horse Mint. (I. F. f. 3177.) Perennial 

 by suckers, canescent or puberulent. 3-8 dm. high. Leaves lanceolate, ovate- 

 lanceolate, or oblong-lanceolate, sessile or short-petioled, acute, sharply serrate, 

 2-8 cm. long ; whorls of flowers in narrow acute spikes, which become 5-13 cm. 

 long in fruit ; bracts lanceolate-subulate ; calyx tomentose or canescent, its teeth 

 subulate, one-half as long as the tube ; corolla puberulent. In waste places, Conn, 

 to Penn. and N. J. Nat. from Europe. July-Oct. 



5. Mentha rotundifolia (L.) Huds. Round-leaved Mint. (I. F. f. 3178.) 

 Perennial by leafy stolons, canescent or tomentose-puberulent, somewhat viscid, 

 3-8 dm. high. Leaves elliptic, or ovate-oblong, short-petioled, or sessile and 

 somewhat clasping by the subcordate or rounded base, obtuse, crenate-serrate, 

 2-5 cm. long, rugose-reticulated beneath ; whorls of flowers in spikes which elon- 



