676 A TEXT-BOOK OF BOTANY. 



Marrubium vulgar e (white hoarhound) is a perennial woolly 

 herb with ascending branches; the leaves and flowering tops are 

 used in medicine. 



Salvia officinalis or garden sage is a perennial, somewhat 

 shrubby, pubescent herb. The leaves are ovate, crenulate. The 

 flowers are bluish, somewhat variegated, the calyx and corolla 

 both being deeply bilabiate. Only the two anterior stamens are 

 fertile (bear anthers) ; the connective is transverse, the upper 

 end bearing a perfect pollen-sac, and the lower a somewhat 

 enlarged rudimentary pollen-sac (Fig. 223, F}. 



Hedeoma pulegioides (American pennyroyal) (Fig. 371). 



MENTHA species. The plants are nearly glabrous, diffusely 

 branching herbs, which form leafy stolons that are perennial 

 (Fig. 184). The leaves and flowering tops of both Mentha 

 piperita (Fig. 372) and Mentha spicata are official. 



2. VOLATILE OILS of the following plants are official : 



Rosmarinus officinalis is a shrub growing in the Mediterranean 

 countries. The plant has linear, coriaceous leaves, and bluish, bila- 

 biate flowers, the middle lobe of the lower lip of the corolla being 

 large, concave, and toothed on the margin. The flowering tops 

 yield from i to 1.5 per cent, of oil which is composed of 15 to 18 

 per cent, of borneol ; about 5 per cent, of bornyl acetate ; and 

 pinene, camphene, camphor, and cineol. There are two commer- 

 cial varieties of the oil, the Italian and French, the latter having 

 the finer odor. 



Lavandula officinalis (garden lavender) is a shrub growing in 

 the Northern Mediterranean countries, as well as in England. 

 The leaves are linear, coriaceous ; the flowers are small, light blue, 

 bilabiate, with a tubular calyx, and occur in opposite cymes 

 (verticillasters). 



The oil is derived from the fresh flowering tops, the flowers 

 yielding about 0.5 per cent. Two kinds of oil are on the market, 

 namely, French and English. The French oil contains 30 to 45 

 per cent, of 1-linalyl acetate; linalool ; geraniol, both of which 

 latter constituents occur free and as esters. The English oil con- 

 tains about 5 to 10 per cent, of linalyl acetate and a slight amount 

 of cineol. Spike lavender (Lavandula Spica} is sometimes dis- 

 tilled with true lavender (see p. 679). 



