120 ORIGIN OF CULTIVATED PLANTS. 



In order to understand the difficulties which it 

 presents, we must first ascertain what nearly allied forms 

 authors designate sometimes as distinct species of the 

 genus Linum, and sometimes as varieties of a single 

 species. 



The first important work on this subject was by 

 Planchon, in 1848. 1 He clearly showed the differences 

 between Linum usitatissimum, L. humile, and L. angus- 

 tifolium, which were little known. Afterwards Heer, 2 

 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 com- 

 parison 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. A nnuum (annual). Root annual; stem single, 

 upright ; capsules 7 to 8 mm. long ; seeds 4 to 6 mm., 

 terminating in a point, a. Vulgare (common). Capsules 

 7 mm., not opening when ripe, and displaying glabrous 

 partitions. German names, Schliesslein, Dreschlein. 

 J3. Humile (low). Capsules 8 mm., opening suddenly when 

 ripe; the partitions hairy. Linum humile, Miller; L. 

 crepitans, Boninghausen. German names, Rlanglein, 

 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 roma- 

 num. 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 



1 Planchon, in Hooker, Journal of Botany, vol. vii. p. 165. 

 3 Heer, Die Pflanzen der Pfahlbauten, in 4to, Zurich, 1865, p. 35 ; Ueler 

 den Flacks und die Flachslcultur, in 4to, Zurich, 1872. 



