5-2 DIDYNAMIA. GYMNOSPERMIA. 



Calix 5-cIeft, subcqual. Anthers approach- 

 ing each other in pairs, each pair producingthe 

 form of a cross. 



Creeping hei-baceous and aromatic plants; peduncles 

 axillary about 3-flowered, flowers blue. Corolla double 

 the length of the calix, upper lip bifid, lower trifid, mid- 

 dle segment larger and emarginate. 



Species. 1. G. hederacea. Probably indigenous; — 

 ahujidant along the banks of the Ojiio, the Potomac, &.c. 

 remote from settlements, flowers larger and brighter 

 than the European species- 



Of this genus there is now a second species described 

 as growing in the woods of Hungary. 



407. MARRUBIUM. L, (White Horchound.) 

 Calix salverforni, rigid, 10-striate. Upper 



lip of the corolla bifid, linear, straight. 



Flowers verticillate, sessile; bractes numerous, linear. 

 Leaves mostly whitisli and rugosely veined. Calix in ma- 

 ny species l6-toothed. 



Species. \. M. vuljare. Naturalized. — .\ small ge- 

 nus principally indigenous to the south of Europe and the 

 Levant. 



408. HYPTIS. Jacquin. 



Calix 5-tootlied. Corolla bilabiate: upper 

 lip 2-lobed; lower 3-lobed: intermediate lobe cal- 

 ceiform, at first involving tlie style and sta- 

 mina, afterwards reflected. Stamina declinate. 



POITEAU. 



Herbaceous; flowers capitate, rarely subcymose pani- 

 culately spiked or axillary; capituli involucrate. 



Species. 1. H. cnpitata. 2. radiata. — A tropical genus 

 indigenous to America, with the exception of H. persica. 



409. PYCNANTHEMUM. Michaux, (Mountain 



Mint.) 



Capitulum surrounded by an involucrum of 

 many bractes.-^Caiix tubular, striate 5-toothed. 

 Upper lip of the corolla nearly entire; lower tri- 



