(9.) _Lepidodendron_ (Messrs Merry and Cunningham's Clayband Iron-Pit, Carluke). Stem 2 inches in diameter. Secondary spirals 18 S, 29 D, 47 S. Divergence = 21/76.
(10.) _Lepidodendron_ (R. B. Garden, Edinburgh, Museum). Stem somewhat flattened, 1-1½ inch in diameter. Secondary spirals 9 D, 14 S, 23 D, 37 S. Divergence = 13/60.
(11.) _Lepidodendron_ (Redhaugh, near Edinburgh, Mr. Peach). Stem somewhat flattened, ¾ to ½ inch in diameter. Secondary spirals 9 S, 14 D, 23 S, 37 D. Divergence = 13/60.
(12.) _Knorria taxina_ (Stockbriggs, Lesmahagow,--Hunterian Museum). About 1 inch in diameter. The specimen consists of a main stem and one of the branches into which it has forked. On the main stem the secondary spirals are 6 D, 11 S, 17 D. Divergence = 5/28 (series, ⅕, ⅙, 2/11, 3/17, 5/28, etc.)--On the branch the secondary spirals are 8 S, 13 D. Divergence = 8/21 (ordinary series, ½, ⅓, ⅖, ⅜, etc.)
E. Series, ½, ⅖, 3/7, 5/12, 8/19, 13/31, 21/50, etc.
(13.) _Lepidodendron_ (from Dr. Rankin's collection). About ⅞ inch in diameter. Secondary spirals 12 D, 19 S, 31 D. Divergence = 21/50.
F. Series, ⅓, 3/10, 4/13, 7/23, 11/36, 18/59, etc.
(14.) _Lepidodendron elegans_ (Possil Ironstone). About 1¼ inch in diameter. Secondary spirals 10 S, 13 D, 23 S, 36 D. Divergence = 18/59.
(15.) _Lepidodendron_ (Possil Ironstone). About 2¼ inches in diameter. Secondary spirals 23 S, 36 D, 59 S, 95 D. Divergence = 47/154.
From the above it is evident that the phyllotaxis of Lepidodendron is extremely variable, as much so perhaps as that of those most variable plants, in this respect, the Cacti. It is also clear that what has been enunciated by Professor Haughton (Manual of Geology, Lond. 1866, pp. 243, 245) as the law according to which the leaves of palæozoic plants were arranged--viz. that of alternate whorls--does not apply to these ancient Lycopods. Lepidodendron aculeatum is noted by Naumann as exhibiting an 8/21 arrangement. (Poggendorff, Annalen, 1842, p. 5.) Professor Alexander Braun (Nov. Acta Ac. C. L. C. xv. 1, pp. 558-9), speaking of the excessive deviation from ordinary arrangements in Equisetaceæ (including Calamites), compares them in this respect with Lycopodiaceæ (including Lepidodendron), saying that in these two families "the utmost limits of the domain of all leaf-arrangement appears to be attained."