The first important work on this subject was by Planchon, in 1848.[580] He clearly showed the differences between Linum usitatissimum, L. humile, and L. angustifolium, which were little known. Afterwards Heer,[581] when making profound researches into ancient cultivation, went again into the characters indicated, and by adding the study of two intermediate forms, as well as the comparison of a great number of specimens, he arrived at the conclusion that there was a single species, composed of several slightly different forms. I give a translation of his Latin summary of the characters, only adding a name for each distinct form, in accordance with the custom of botanical works.
Linum usitatissimum.
1. Annuum (annual). Root annual; stem single, upright; capsules 7 to 8 mm. long; seeds 4 to 6 mm., terminating in a point. α. Vulgare (common). Capsules 7 mm., not opening when ripe, and displaying glabrous partitions. German names, Schliesslein, Dreschlein. β. Humile (low). Capsules 8 mm., opening suddenly when ripe; the partitions hairy. Linum humile, Miller; L. crepitans, Böninghausen. German names, Klanglein, Springlein.
2. Hyemale (winter). Root annual or biennial; stems numerous, spreading at the base, and bent; capsules 7 mm., terminating in a point. Linum hyemale romanum. In German, Winterlein.
3. Ambiguum (doubtful). Root annual or perennial; stems numerous, leaves acuminate; capsules 7 mm., with partitions nearly free from hairs; seeds 4 mm., ending in a short point. Linum ambiguum, Jordan.
4. Angustifolium (narrow-leaved). Root annual or perennial; stems numerous, spreading at the base, and bent; capsules 6 mm., with hairy partitions; seeds 3 mm., slightly hooked at the top. Linum angustifolium.
It may be seen how easily one form passes into another. The quality of annual, biennial, or perennial, which Heer suspected to be uncertain, is vague, especially for the angustifolium; for Loret, who has observed this flax in the neighbourhood of Montpellier, says,[582] “In very hot countries it is nearly always an annual, and this is the case in Sicily according to Gussone; with us it is annual, biennial, or perennial, according to the nature of the soil in which it grows; and this may be ascertained by observing it on the shore, notably at Maguelone. There it may be seen that along the borders of trodden paths it lasts longer than on the sand, where the sun soon dries up the roots and the acidity of the soil prevents the plant from enduring more than a year.”
When forms and physiological conditions pass from one into another, and are distinguished by characters which vary according to circumstances, we are led to consider the individuals as constituting a single species, although these forms and conditions possess a certain degree of heredity, and date perhaps from very early times. We are, however, forced to consider them separately in our researches into their origin. I shall first indicate in what country each variety has been discovered in a wild or half-wild state. I shall then speak of cultivation, and we shall see how far geographical and historical facts confirm the opinion of the unity of species.
The common annual flax has not yet been discovered, with absolute certainty, in a wild state. I possess several specimens of it from India, and Planchon saw others in the herbarium at Kew; but Anglo-Indian botanists do not admit that the plant is indigenous in British India. The recent flora of Sir Joseph Hooker speaks of it as a species cultivated principally for the oil extracted from the seeds; and Mr. C. B. Clarke, formerly director of the botanical gardens in Calcutta, writes to me that the specimens must have been cultivated, its cultivation being very common in winter in the north of India. Boissier[583] mentions L. humile, with narrow leaves, which Kotschy gathered “near Schiraz in Persia, at the foot of the mountain called Sabst Buchom.” This is, perhaps, a spot far removed from cultivation; but I cannot give satisfactory information on this head. Hohenacker found L. usitatissimum “half wild” in the province of Talysch, to the south of the Caucasus, towards the Caspian Sea.[584] Steven is more positive with regard to Southern Russia.[585] According to him, it “is found pretty often on the barren hills to the south of the Crimea, between Jalta and Nikita; and Nordmann found it on the eastern coast of the Black Sea.” Advancing westward in Southern Russia, or in the region of the Mediterranean, the species is but rarely mentioned, and only as escaped from cultivation, or half wild. In spite of doubts and of the scanty data which we possess, I think it very possible that the annual flax, in one or other of these two forms, may be wild in the district between the south of Persia and the Crimea, at least in a few localities.
The winter flax is only known under cultivation in a few provinces of Italy.[586]