This section is from the book "A Text Book Of Materia Medica, Being An Account Of The More Important Crude Drugs Of Vegetable And Animal Origin", by Henry G. Greenish. Also available from Amazon: A Text Book of Materia Medica : Being an Account of the More Important Crude Drugs of Vegetable and Animal Origin.
The couch grass, Agropyron repens, Beauvais (Tri-ticum repens, Linne, N.O. Gramineoe), is abundant in this country, being often a troublesome weed. It produces a slender rhizome, running for a considerable distance just below the surface of the ground, giving off lateral branches, and at the nodes, which are 2 to 3 cm. apart, small fibrous roots. The rhizome, which appears to have been used by the Greeks and Romans for certain affections of the bladder, is collected, cut into pieces about 1 cm. long, and dried.
Fig. 214. - Couch Grass rhizome and transverse section; the latter magnified 3 diam. (Maisch).
Couch grass is generally met with in commerce cut into short pieces. The rhizome is very slender, averaging about 2 mm. in diameter, and of a dark straw-yellow colour. The surface is quite glabrous, hard and shining and usually bears five or six rather prominent longitudinal ridges. Some of the pieces bear the nodes, at which there may be found the persistent fibrous remains of a sheathing leaf-basis, and either a few threadlike paler roots or the scars left by them. The transverse section exhibits, under a lens, a narrow pale inner ring (the stele), hollow in the centre, surrounded by a darker translucent cortex.
The drug has but little odour, and a sweetish, mucilaginous taste.
The student should observe
(a) The slender hollow rhizome,
(b) The translucent (not starchy) cortex.
Couch grass contains a carbohydrate, triticin (5 per cent.), which is not very soluble in water, and yields by hydrolysis levulose; it appears to occur in the rhizomes of other Graminaceous plants, and possibly is widely diffused in the vegetable kingdom.
Mucilage, inosite, and levulose are also constituents of the rhizome, but starch is not present.
Most of the commercial drug is imported from the Continent and frequently consists of the rhizome of Cynodon Dactylon, Persoon. This contains abundance of starch which affords a ready means of distinguishing it; the section is white and is blackened by solution of iodine.
Couch grass has been employed as a diuretic in certain affections of the bladder.