Silphium Laciniatum, Lin., Rosin Weed.

Botanical name: 

Natural order, Compositae; Sub-order, Tubuliflorae; Sub-tribe, Melampodineae.


From an Inaugural Essay.

Rosin weed, or compass plant, is found growing extensively westward from Ohio, between 38° to 46° north latitude.

The stem is usually three to six, but sometimes reaches the height of ten feet, and bears, along its entire length, leaves similar to the radical, but gradually becoming smaller toward the apex. The flowers, borne in a kind of raceme at the upper part of the stem, are two to three inches broad, and, as in all the other species, yellow; the scales of the involucre are ovate, tapering into long and spreading rigid points; achenia broadly winged and deeply notched. There arise from the root numerous radical leaves, which are from ten to thirty inches in length, very rough with bristly hairs, in general outline ovate, but deeply pinnately cut and parted, the divisions themselves very often cut-lobed. The root is from one to three feet in length, and one-half to two inches in diameter, and has a very rough and irregular cortical layer. Its anatomical structure is as follows:

Silphium root, Figs. A, C, and D. Silphium root, Fig. B: Longitudinal section of roo...
ROOT OF SILPHIUM LACINIATUM.—A Transverse section, magnified, with origin of a rootlet. C Pitted duct. D Transverse section, natural size.
Fig. B, is a longitudinal section of the root, and shows the very irregular course of the simple resin ducts.
Fig. C shows one of the pitted ducts, which were the only kind found, although some twenty specimens of the root were examined.
Fig. D is a cross section of the root, natural size, from which the different magnified sections were cut.

Fig. A shows a cross section of the root; the inner portion, comprising one-sixth of the radius of the root, is the pith (p) and is composed of loose parenchyma cells; we then find two circles of resin (cc) ducts, the inner circle near the dividing line of the woody tissue (w) and the pith, and the outer circle between the wood wedges (w) and the outer layer of parenchyma (d) tissue. These resin ducts are very irregular in shape.

The woody zone between the two rows of resin ducts is traversed by very wide medullary rays; the wood wedges are irregular in shape, and at the head of each is a wedge-shaped bundle of sieve (s) tubes, reaching to the outer row of resin ducts. Between the outer row of resin ducts and the cortical (b) layer is found a narrow layer of parenchyma cells, which are more compressed as they near the cortical layer, and this latter is composed of very irregular compressed tissue, resembling stone cells, and is of a yellowish-green color.

a shows the development of a rootlet; most of the rootlets originate from the inner row of resin ducts.

Following is the result of an analysis made of the resinous juice which exudes from the stem and foliage of the plant, either spontaneously or from the puncture of insects. It congeals in small translucent, and internally transparent, light yellow tears, of varied forms, breaks with a conchoidal fracture, has an agreeable terebinthinous odor and taste, softens quickly in the mouth, and is easily masticated and kneaded between the teeth; it has the specific gravity 1.039 at 20°C., and upon incineration one gram yielded 6.005 gram or 0.5 of ash.

On treating an excess of the oleoresin with different liquids the following results were obtained, showing the relative solvent power of 100 parts of the liquids: chloroform 24.2, carbon disulphide 23.6; ether 19.3, benzin 18.0, benzol 17.0, alcohol of 90 per cent. 15.2, methyl alcohol 10.2 parts of the constituents of the exudation.

On the spontaneous evaporation of these solutions no crystalline residue was left. The residue left after the evaporation of the alcoholic solution was a yellowish-white waxy mass, with minute transparent globules covering its surface, and which upon examination proved to be volatile oil. A small portion (0.62 per cent of the oleoresin is soluble in water. Chloroform dissolves nearly the whole of the oleoresin, which is insoluble in glycerin.

Subjected to distillation with water, a colorless volatile oil was obtained, having the specific gravity 0.868 at 18°C. It is neutral to test paper, soluble in equal parts of 90 per cent. and in fifteen parts of 80 per cent. alcohol, and boils at 158°C. It has a distinct terebinthinous odor, and with iodine gives quite a violent action, generating considerable heat. After carefully freeing a portion from water with chloride of calcium it gave a very slight action when brought in contact with metallic sodium, the oil doubtless consisting of a hydrocarbon probably identical in composition with oil of turpentine. The sodium was left in contact with the oil for several days without perceptibly changing its odor, but the oil assumed a light yellowish color.

The watery liquid left in the retort on the distillation of the volatile oil contained sugar, and yielded after some time a brownish precipitate with ferric chloride and white precipitates with caustic alkalies and with the lead acetates.

The residue left in the retort, after complete exhaustion with watery was a brownish-white mass, having an odor while warm very much like that of copaiba. It was completely soluble in chloroform, while carbon disulphide dissolved 97.1 per cent., ether 78.4 per cent., benzin 72.7 per cent. and alcohol (90 per cent.) 5.40 per cent. of it.

The portion soluble in alcohol, after spontaneous evaporation, was obtained in the form of a yellowish extract. It was wholly soluble in chloroform, almost entirely soluble in carbon disulphide, benzin and ether, which solutions by evaporation left residues of the same amorphous character.

The part insoluble in alcohol is whitish, tasteless, falls to powder when rubbed between the fingers, and is wholly soluble in chloroform and carbon disulphide, and only partly soluble in benzin and ether, and upon the evaporation of the liquids was again obtained as an amorphous powder.

A portion of the resinous residue from the retort was soluble in potassa and in ammonia, and reprecipitated by acids, and consists probably of a resinous acid.

Some of the residue was fused with caustic potash, the fused mass extracted with water, filtered, acidulated with sulphuric acid, the solution concentrated and the sulphate of potassium for the most part separated by crystallization; the filtrate was then well shaken with ether, the ether separated and allowed to evaporate spontaneously, when a whitish residue was left. This tested with ferric chloride did not change color, showing that there was no protocatechuic acid formed by this treatment.

The oleoresin which is gathered by children for chewing gum resembles mastich very much in appearance, but is much less soluble in alcohol, and its constituents seem to be more nearly allied to those of Chian turpentine.

The only part of the plant generally used is the leaves, and a fluid extract prepared therefrom is found in the market. The powdered leaves have also been used in cattle powder as a diuretic.

The oleoresin yielded 19.66 per cent. of volatile oil and 37 per cent of acid resin, the other constituents being wax, sugar, an undetermined white powder and a small amount of inorganic constituents.

The American Journal of Pharmacy, Vol. 53, 1881, was edited by John M. Maisch.