194 PLANT ORGANS OR PARTS OF PLANTS. 



'I'hc leaf mcsopliyll is made up of irregular parenchy- 

 matic tissue, some palisade cells with chlorophyll, and 

 many cells contain isolated aggregated crystals of calcium 

 oxalate. A few rhomboid, tabular crystals may also be 

 at times found, though they are few and readily over- 

 looked. The tissues from the nerves and petioles con- 

 tain V)ast fiV)res, few in number; tracheids, a few spiral 

 and annular ducts, and occasionally scalariform ducts. 



The oil glands are usually situated just beneath the 

 epidermis of the leaf, either upper or under surface. The 

 crystals have been mentioned as occurring in the meso- 

 phyll; starch is usually rare, the granules are, as a rule, 

 simple, rarely compound, with centric hilums, and vary 

 from 6 to lo microns. 



The hairs are very few. They arc characteristic, 

 however, long and curved, and are apt to be irregularly 

 thickened towards the apex. Small stone cells sometimes 

 occur in the petiole of the leaf.* 



Chemistry.— The leaves contain about one-half per 

 cent, of ethereal oil and two alkaloids, pilocarpine and 

 jaborine. 



MENTHA PIPERITA. PEPPERMINT. 



Mentha piperita, peppermint, is the leaves and tops of 

 Mentha piperita, a small herbaceous plant widely culti- 

 vated in gardens. 



Fluckiger states t that it docs not resemble any known 

 indigenous mint of Europe, and quotes Bentham as stat- 

 ing that peppermint is probably derived from the wild 

 form, Mentha hirsuta, L. 



Description. — The plant is a low perennial, two to 



♦Two important rcscarchcH have recently appeared upon the leaves: 

 of pilocfirpuH, that of Geiger, published in the "Berichte der Deutschen 

 Pharmaceutischcn GeBcllschaft," 1896, and the other from the Pharma- 

 cognosy Laboratory of the New York College of Pharmacy, by A. 

 Schneider, "Journal of Pharmacology," vol. 4, 1897, p. m- 



t I'harmakognosic des Pflanzenreiches. 



