Mexican Lign Aloes.
By E. M. HOLMES, F.L.S.,
Curator of the Museum of the Pharmaceutical Society.
Although the essential oil bearing the above name has been a commercial article for many years, and was noticed in the columns of this journal by Mr. J. Collins as long ago as 1869, yet nothing definite has been ascertained concerning its botanical source until quite lately. Three years ago a description of the tree yielding the oil was published by M. Poisson in the Bull. de l'Assoc. Franc. pour l'Avancement des Sciences, xiii., p. 305, pl. x. (Blois, 1884), but in consequence of the difficulty of access to this publication it has been overlooked even by the authors of the 'Biologia Centrali-Americana,' and it was only during a recent visit of Professor Baillon to the Museum of the Pharmaceutical Society that my attention was called by him to the article in question. It seems desirable, therefore, to place on record in this Journal an abstract of that paper.
M. Poisson was led to inquire into the botanical source of the product through seeing specimens of the wood and oil at the Paris Exhibition of 1878, where these products were exhibited by Messrs. Ollivier and Rousseau, of Paris. These gentlemen obtained specimens of the leaves, flowers and fruit from their correspondent in Mexico, M. Delpech, in whose honor the tree has been named by M. Poisson. The description he gives of the tree is as follows:
"Bursera Delpechiana.—Foliis apice ramulorum congestis, tenuibus novellis utrinque, imprimis subtus, costis et nervis tenuiter pilosis, 3 jugis; foliolis ellipticis, utrinque acutis, crenato-serratis; interstitiis inter juga anguste alatis; paniculis folia aequantibus breviter pilosis, compositis, laxifloris, bracteolis angustissime linearibus, pedicellis tenuissimis, calycis lobis brevibus deltoideis atque petalis oblongis 5 poll. longioribus, sparse et longe pilosis, staminibus quam petala paullo brevioribus, filamentis quam antherae oblongo-ovatae 4 poll. longioribus; drupis ovoideis glabris."
"Folia 5-6 cent. longa, interstitiis interjugalibus 7-8 mill. longis, 1-1 ½ mill. latis; foliola 1 ½ -2 cent. longa, 8-10 mill. lata, nervis lateralibus 1 ½ -2 mill. distantibus. Paniculae (e eymis compositae) axillares numerosae 5-7 cent. longae, ramulis secundariis 1 ½ -2 cent. longis, pedicellis 3-4 mill. aequantibus, bracteolis tenuissimis 2-4 mill longis. Calycis lobi vix 1 Mill. longi. Petala (aestivatione valvata) 4 mill. longa, 1 mill. lata. Staminum filamenta 3 m. longa, antherae vix 1 mill. aequantes. Drupae fere 1 cent. longae. Mexico circa urb. diet. Cuantla Morelos."
The species is characterized by the excessive brevity of the calyx, of which the lobes are not well marked. It belongs to the set of species peculiar to Mexico, including B. Aloexylon, Engl., and B. penicillata, Engl. The tree is of medium height. According to M. Delpech, the wood in a fresh and healthy state is almost devoid of odor, and it is only where a branch has been broken off or insects have pierced the wood that the oil becomes developed. He states that old trunks may afford as much as 10 to 12 per cent. of oil. This difference in the wood is not recognized by the native Indians who collect it, and consequently the tree is felled in a reckless manner, so that it has almost disappeared from Cuantla Morelos, where it formerly abounded. The pure oil is obtained by M. Delpech by distillation by steam, heat, and costs 20 to 25 francs per kilogram; an inferior oil prepared by the natives is sold for a lower price.
The structure of the wood presents the following characters. The fibres are of medium length with the walls only slightly thickened; each is divided transversely by numerous thin walls constituting a kind of ligneous parenchyma, of which the whole wood is formed. On transverse section the fibres are seen to be all of equal thickness, so that it is not easy to distinguish the zones of growth of the wood.
The vessels are of large size, with numerous transverse trabeculae, which on longitudinal section are seen to give a moniliform. appearance to the vessels; they are dotted all over, the dots being surrounded with areolae.
The medullary rays are thin, and have two to four courses of cells in thickness. It is chiefly in the fibres and medullary rays that the nearly solid odorous substance occurs. It is of a yellowish resinoid aspect under the microscope, and fills them either wholly or partially. All the fibres, however, do not contain it, and it is most abundant where the wood is streaked with dark veins. This matter is soluble in alcohol, so that the wood treated with spirit becomes transparent under the microscope. In the green and healthy state the wood presents the same appearance, without any trace of oil, although at the same time the oil may be perceived in the fruits and bark by rubbing them. In M. Léon Marchaud's memoir on the "Organization of the Burseraceae," a somewhat similar occurrence is mentioned. The resinous and perfumed matter of Balsamodendron Myrrha, B. africanum and Protium obtusifolium is localized in the pith of the young branches to some degree, but is abundant in the bark and pericarp of the fruits of these plants.
The oil of lign aloes has been examined by Messrs. Verneuil and Poisson. Their experiments show that the wood cut into shavings readily yields the oil by distillation with steam, 7 to 9 per cent. being thus obtained, and the wood when dry is then found to be free from odor.
When the oil is dried over chloride of calcium, it distils over almost entirely between 189° and 192°, a small quantity of a resinous body of a much less volatile character remaining in the still. It is an oxygenated body having the formula 2 (C10H8) 5 H2O, this formula answering to that of a hydrate of terebenthene or of an insomer. The oil slowly absorbs oxygen and becomes resinified. It does not combine with bisulphite of sodium. The red-brown coloration which it takes under concentrated sulphuric acid is analogous to that which turpentine produces with the same acid. The odor of the oil is likened by M. Poisson to a mixture of lemon and jasmin. The specimens that I have seen have more resemblance to bergamot in odor.
It is difficult to say whether other species of Bursera yield this oil or no. M. Poisson suggests that it is probably obtained also from Bursera, Aloexylon, Engl. (Elaphrium Aloexylon, Sebiede).
The new Mexican Pharmacopoeia (1884), p. 75, also gives Amyris linaloe, La Llave, which is a synonym of Bursera Aloexylon, Engl., as the source of the oil.
Schlechtendal, however, in 'Linnaea' (1843), xviii., p. 303, remarks that this species has a fennel-like odor. A specimen in the Kew Herbarium, presented by Mr. Piesse as the Lignaloe plant, is labelled "Elaphrium graveolens, K.," from the West coast of N. Mexico. This identification is, however, according to Professor Oliver, somewhat uncertain. Several other species of Bursera grow in the same district, as B. Delpechiana, including B. bicolor, Engl., B. Schiedeana, Engl., and B. jorullensis, Engl., but nothing appears to be known about the oil of these trees. Schlechtendal mentions, l. c., that Elaphrium glabrifolium (=Bursera penicillata, Engl.) has a strong aromatic odor, and that Amyris ventricosa (=Bursera fagaroides, Engl. var.) has an odor of caraways. The Mexican species of the genus appear to be very numerous, and require further examination as to their economic products. It is , however, satisfactory to be able to refer Mexican oil of lign aloes with certainty to one species, for there can be no doubt that B. Delpechiana, is one of the principal sources of it.—Phar. Jour. and Trans., Aug. 13, 1887, p. 132.