32 DIDYNAMIA. GTMNOSPERMIA, 



Calix 5-cJcI't., subtqual. Jiiithers approacli- 

 ing each other in pairs, each pair producing the 

 form of a cross. 



Creeping herbaceous and aromatic plants; peduncles 

 axillary about 3-i^owered, fiowtrs blue. Corolla double 

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

 dle segment larger ai^d emarginate. 



Spicies. 1. r.. hederacea Probably indigenous; — 

 abundant along the bai.ks of the Ohio, the Potomac, S^c. 

 remote from se'tlemcrsts, flcv/ers 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, (Whire Horehoun^l.) 

 Calix salverform, rigid, 10-striate. Upper 



lip of the coroWa bitid, linear, strai.grht. 



Flowers vcrticillale, sessile; bractes numerous, linear, 

 Leaves mostly whitish and rugobely veined. Calix in ma- 

 ny species l6-toothed. 



Species. 1. M. vulgare. Naturalized. — .\ small ge- 

 nus principally indigenous to the south of Europe and the 

 Levant. 



408. KYPTIS. Jacquin, 



Calix 5-toothed. Corolla bilabiate: upper 

 lip 2-lobed,* lower 3-lobed: intermediate lobe cal- 

 ceiform, at first involvini^ tlie style and sta- 

 mina, afterwards reflected. Stamina declinate. 



PolTEAU. 



Herbaceous; flowers capitate, rarely subcymose pani- 

 culately spiked or axillary; capituli involucrate. 



Species. 1. H. cnpitata. 2- radiata. — A tropical genits 

 indigenous to Americai with the exception of H. persica. 



409. PYCNANTHEMUM. Mkliaux, (Mountain 

 Mint.) 



Capitulum surrounded by an involucrum of 

 many bractes. — Calix tubular, striate 5-tonthcd. 

 Upper lip of the corolla nearly entire; lower tri- 



