222 American Midland Naturalist Monograph No. 7 



27. Cunila L. — Stone Mint 

 C. origanoides (L.) Britt. Wooded ridges in southern 111. Aug.- 

 Oct. 



28. Lycopus L. — Water Horehound 

 1. Calyx-teeth lanceolate, shorter than or equalling the mature 

 nutlets; leaves serrate, not incised. 

 2. Base of plant and stolons lacking tubers; nutlets sharply muri- 

 cate on top, 1.7-2 mm long at maturity; wet ground, not 

 infrequent. July-Oct L. virginicus L. 



2. Base of rhizome and tips of stolons often bearing a tuber ; 



nutlets smooth or merely rugulose on top, 1-1.5 mm long 

 when mature; moist ground in the northern part of the 

 state, extending southward to Tazewell and Champaign 



counties. Aug.-Sept L. utnflorus Michx. 



1. Calyx-teeth subulate, much longer than the nutlets. 



3. Lower leaves petiolate. 



4. Leaves dentate or coarsely serrate; corolla 2-3 mm long, 

 twice the length of the calyx; wet ground, locally through- 

 out 111., except the northern counties. Aug.-Sept 



- L. ruhcllus Moench 



4. Leaves (at least the lower) more or less incised or sinii- 

 ately pinnatifid; corolla slightly longer than the calyx; 

 wet ground, the common species throughout 111. July- 

 Sept. [L. sinuatus Ell.] L. americanus Muhl. 



3. Lower leaves sessile; waste ground, not common; known from 

 Bureau, Whiteside, Cook, Henry, and Lake counties. July- 

 Aug L. aspcr Greene 



29. Mentha L. — Mint 

 ] . Whorls of flowers mostly in terminal spikes. 

 2. Stem glabrous or nearly so. 



3. Leaves sessile or subsessile; calyx 1-1.5 mm long; moist 

 ground, occasional; nat. from Eur. July-Sept. Spearmint 

 - M. spicata L. 



3. Leaves all distinctly short-petioled ; calyx 2-3 mm long; waste 



places and along roads; nat. from Eur. July-Sept. Pepper- 

 mint M. piperita L. 



2. Stem pubescent, at least at the nodes. 



4. Spikes slender, less than 1 cm thick, often interrupted; leaves 



rugose, roimdish-ovate, finely pubescent and reticulate be- 

 neath; waste ground, rarely escaped from cult.; nat. from 



Eur. Roimd-leaved Mint M. rotundijolia (L.) Huds. 



4. Spikes 1 cm thick, dense. 



5. Leaves sessile, not crisped; stem and calyx finely pubescent; 

 roadsides and waste places, occasional; introd. from Eur. 



Woolly Mint M. alopecuroides Hull 



5. Leaves crisped, wavy, short-petioled; calyx nearly gla- 

 brous; roadsides and waste places, escaped from cult.; 

 native of Eur. July-Sept. Crisp Mint M. crispa L. 



