[178] Figures taken from Bulletin 169, Calif. Expt. Station, June, 1905.
[179] See Bulletin No. 16 of the Wyoming Experiment Station; also Bulletin Nos, 2 and 12 of the Division of Agrostology, and Farmers’ Bulletin No. 108, U. S. Department of Agriculture.
[180] Analyses made at the California station show 19.37 percent of ash in the air-dry matter of Australian saltbush. (See California Station Bulletin No. 105; E. S. R., vol. 6, p. 718). Analyses of Russian thistle have been reported showing over 20 per cent of ash in dry matter. (See Minnesota Sta. Bulletin No. 34; Iowa Sta. Bull. No. 26; E. S. R., vol. 6, pp. 552-553).
[181] It should be understood that the plants so referred to are exclusively the true grasses, recognized as such by every child, and not forage plants generally; which are sometimes so designated; not only by farmers, but by some authors who fail to appreciate the practical importance of the distinction, which makes it necessary that farmers should be taught to understand it.
[182] Report on Cotton Culture; 10th Census of the United States, vol. 5, pp. 23 to 34.
[183] The special object of this chapter as a whole has seemed to the writer to require a repetition of much that is already said in the preceding chapters.
[184] [See above, pp. 313 to 315, chapter 18].
[185] Such lists, so far as the State of Mississippi is concerned, may be found in the writer’s Report on the Agriculture and Geology of Mississippi, 1860. See also Plant Life of Alabama, by Charles Mohr.
[186] “A lime country is a rich country.”
[187] R. M. Harper, who has graphically described the vegetative features of the coastal plain of Georgia (Contr. from the Dep. of Bot. Colum. Univ. Nos. 192, 215, 216, 1902-05; also Bull. Torr. Bot. Club 29-32), claims the deciduous cypress of the wet pine-barrens and ponds therein, the vegetation of which greatly resembles that of the pine meadows of the Mississippi sea-coast, to be a distinct species, Taxodium imbricarium, the leaves of which are imbricated, instead of two-ranked and with spreading leaflets. He supports this distinction mainly by the differences in habit from the Louisiana swamp cypress, and the fact that the imbricated form occurs wholly on non-calcareous land, while the other is at home in the calcareous alluvial areas. The imbricated form has been observed and commented on before, as a mere ecological variation, and in the writer’s opinion this is all that can be claimed, in view of the much greater differences in the form of other trees, notably oaks, illustrated below, caused also by lime. There would, à fortiori, be reason for claiming at least three different species of post oak and black-jack (and two of willow oak), which differ not only in tree form but also in the form and number of leaf lobes, and yet can be traced into one another by innumerable transition forms. If new species are to be established on such grounds, it is hard to see where the variations manifestly due to environment are to come in.