LAMIACEAE. 255 



4. L. sessilifolius A. Gray. Stems 2-6 dm. tall: leaf -blades ovate to oblong 

 or lanceolate, 1.5-6 cm. long, shallowly serrate: calyx 2-2.5 mm. long; lobes 

 as long as the tube: lower corolla-lip with a reniform notched middle lobe: 

 filaments pubescent at the base. Rare, in low grounds. 



5. L. americanus Muhl. Stems 1-9 dm. tall, often much-branched: leaf- 

 blades lanceolate to ovate-lanceolate, 2-10 cm. long, those on the lower part 

 of the stem pinnatifid, those near the top merely toothed: calyx 2.5-3 mm. 

 long; lobes rather shorter than the tube: corolla about as long as the calyx: 

 staminodia thickened at the tip. Common, in moist thickets and pastures. 



26. MENTHA [Tourn.] L. Perennial erect or diffuse herbs. Leaf- 

 blades toothed or incised. Flowers in dense axillary cymes, these sometimes 

 disposed in spike-like panicles. Calyx nearly regular, the lobes shorter than the 

 tube. Corolla obscurely 2-lipped: upper lip mostly notched: lower lip of 3 

 nearly equal lobes. Stamens 4. Sum. MINT. 



Flower-clusters all axillary. 



Upper leaves or bracts subtending the flower-clusters much smaller than the 



lower leaves. 1. M. Cardiaca. 



Upper leaves or bracts subtending the flower-clusters only 



slightly smaller than the lower leaves. 

 Stem and branches glabrous or with short scattered 

 hairs : calyx glabrous or nearly so, except for the 

 ciliate lobes. 2. M. gentilis. 



Stem and branches with retrorse or spreading hairs : 



calyx pubescent all over. 



Stem and branches with short retrorse or retrorse- 

 appressed hairs : larger calyx-lobes deltoid ; calyx- 

 tube closely pubescent with short hairs. 3. if. arvensis. 

 Stem and branches with long lax or spreading 

 hairs : larger calyx-lobes typically lanceolate : 

 calyx-tube loosely pubescent with long hairs. 4. M. canadensis. 

 Flower-clusters, at least most of them, aggregated in terminal 



spike-like panicles. 



Flowers in short and stout raceme-like panicles, or clus- 

 tered in the upper leaf-axils : longer calyx-lobes decidedly 

 shorter than the tube : leaf-blades petioled. 5. M. piperita. 



Flowers in slender or relatively slender, often elongate 

 spike-like panicles : longer calyx-lobes as long as the 

 tube or nearly so : leaf -blades sessile. 

 Stem and inflorescence not canescent : calyx-tube gla- 

 brous or nearly so : corolla-tube not exceeding the 

 calyx. 6. M. viridis. 



Stem and inflorescence canescent : calyx-tube copiously 



pubescent : corolla-tube much exceeding the calyx. 7. M. alopecuroides. 



1. M. Cardiaca Gerarde. Stems 1.5-5 dm. tall, finely pubescent: leaf -blades 

 lanceolate, oblong-lanceolate, or ovate, 1-5 cm. long, sharply serrate, sometimes 

 incised, the floral ones conspicuously reduced: calyx 1.5-2 mm. long; tube 

 finely pubescent : corolla pink, 45 mm. long. Rather common, in waste 

 grounds. Nat. of Eu. 



2. M. gentilis L. Stems 2-7 dm. tall, glabrous or nearly so: leaf -blades oval, 

 ovate, obovate, or elliptic, 1.5-5 cm. long, serrate, the floral ones not con- 

 spicuously reduced, with petioles often longer than the flower-clusters: calyx 

 1.5-2 mm. long; tube glabrous or nearly so: corolla deep-pink or lilac; upper 

 lip notched. M. Common, in waste places and on roadsides. Nat. of Eu. 



3. M. arvensis L. Plant 4 dm. tall or less, often diffuse, the stem copiously, 

 often closely pale-pubescent: leaf -blades ovate, oblong, or oval, 1.5-5 cm. 

 long, coarsely serrate above the middle, copiously pubescent with short hairs, 

 broad at the base: calyx 1.5-2 mm. long, minutely pubescent; lobes short- 

 tipped: corolla usually pink, mostly 3 mm. long, the upper lip mostly notched. 

 M. Frequent, in and about swamps. Nat. of Eu. 



4. M. canadensis L. Stems 2-6 dm. tall, loosely pubescent: leaf -blades lance- 

 olate, oblong, elliptic, or oblong-lanceolate, 2-7 cm. long, serrate, narrow-based, 



