4 



€hap. IX. WHEAT. 317 



of Heer, 41 that the inhabitants of Switzerland, even so early 

 as the Neolithic period, cultivated no less than ten cereal 

 plants, namely, five kinds of wheat, of which at least four are 

 commonly looked at as distinct species, three kinds of barley, 

 a panicum, and a setaria. If it could be shown that at the 

 earliest dawn of agriculture five kinds of wheat and three of 

 barley had been cultivated, we should of course be compelled 

 to look at these forms as distinct species. But, as Heer has 

 remarked, agriculture even at the period of the lake-habitations 

 had already made considerable progress; for, besides the ten 

 cereals, peas, poppies/ flax, and apparently apples, were cultivated. 

 It may also be inferred, from one variety of wheat being the so- 

 called Egyptian, and from what is known of the native country 

 of the panicum and setaria, as well as from the nature of the 

 weeds which then grew mingled with the crops, that the lake- 

 inhabitants either still kept up commercial intercourse with 

 some southern people or had originally proceeded as colonists 

 from the South. 



Loiseleur-Deslongchamps 42 has argued that, if our cereal 

 plants had been greatly modified by cultivation, the weeds which 

 habitually grow mingled with them would have been equally 

 modified. But this argument shows how completely the prin- 

 ciple of selection has been overlooked. That such weeds have 

 not varied, or at least do not vary now in any extreme degree, 

 is the opinion of Mr. H. 0. Watson and Professor Asa Gray, 

 as they inform me; but who will pretend to say that they 

 do not vary as much as the individual plants of the same 

 sub-variety of wheat? We have already seen that pure 

 varieties of wheat, cultivated in the same field, offer many 

 slight variations, which can be selected and separately propa- 

 gated ; and that occasionally more strongly pronounced varia- 

 tions appear, which, as Mr. Sheriff has proved, are well 

 worthy of extensive cultivation. Not until equal attention be 

 paid to the variability and selection of weeds, can the argu- 

 ment from their constancy under unintentional culture be of 

 any value. In accordance with the principles of selection we 

 can understand how it is that in the several cultivated varieties 

 of wheat the organs of vegetation differ so little ; for if a plant 

 41 « Pflanzen der Pfahlbauten,' 1866. « t L es Ce'reales ' p. 94. 



