572 SCIENTIFIC AND APPLIED PHARMACOGNOSY 



tubular, about 5 mm. in length, ovoid or slightly curved on the lower 

 side near the base, bilabiate, upper lip 3-toothed, lower lip with two 

 linear-lanceolate divisions, 13-nerved, longitudinally striate, pubes- 

 cent; corolla about the size of the calyx, purplish, pubescent, upper 

 lip erect, flat, emarginate, the lower spreading and 3-lobed; fertile 

 stamens two, exserted, ascending, the sterile upper pair rarely with 

 anthers. Nutlets nearly spheroidal or ovoid, about 0.5 mm. in 

 diameter; odor strongly aromatic; taste aromatic. 



Inner Structure. The leaves have a bi-facial structure; the 

 epidermal cells are undulate, except over the veins where the walls 

 are nearly straight; the non-glandular hairs are uniseriate, curved 

 and pointed, consisting of from 1 to 3 cells, having a striated cuticle; 

 the glandular hairs are of 2 types having short stalks and either a 

 2- or 8-celled glandular head. The stomata are broadly elliptical 

 having a pair of subsidiary cells transverse to the pores, the cells of 

 the stomata frequently contain large sphero-crystals. In the young 

 internodes of the stems the outline of the stele is circular in transverse 

 sections, in contrast with the quadrangular outline of the cortex, 

 while in the older stem portions the stele becomes gradually 

 quadrangular by the continued divisions of the interfasicular 

 cambium. There is no ring of sclerenchyma in the pericycle and the 

 endodermis consists of large, thin-walled cells which are free from 

 starch. 



Powder. Dark green; non-glandular hairs slightly curved, 2- 

 to 3-celled, thick walled, with numerous slight centrifugal projections; 

 glandular hairs with 1-celled stalk and 2- to 8-celled glandular head; 

 pollen grains somewhat spheroidal, about 0.035 mm. in diameter, 

 nearly smooth; tracheae spiral or with simple and bordered pores; 

 sclerenchymatous fibers long, thin-walled, lignified, with numerous 

 simple pores; epidermal cells having sphero-crystals or irregular 

 masses of a carbohydrate. 



Constituents. Volatile oil, a bitter principle and tannin. The 

 dried leaves yield about 3 per cent of volatile oil, while the dried 

 stems and leaves yield only 1.3 per cent. The volatile oil is official 

 and consists chiefly of a ketone pulegone, which gives the oil its 

 peculiar properties. The oil also probably contains two other 

 ketones: (a) hedeomol and (6) another resembling menthone. Sev- 

 eral acids have also been found in this oil: formic, acetic and iso- 

 heptylic. 



Allied Plants. Mentha Pulegium, or EUROPEAN PENNYROYAL, 

 apparently contains principles similar to the American pennyroyal, 

 and is distinguished from the latter by the more or less oval, serrate 



