Cette étude en paléobotanie explore l'anatomie et l'évolution de *Sigillaria*, un genre de plantes éteintes, en se concentrant sur les faisceaux vasculaires fossilisés et leur rôle dans la structure foliaire.
1915 x 1305 px | 32,4 x 22,1 cm | 12,8 x 8,7 inches | 150dpi
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. Studies in fossil botany . Paleobotany. SIGILLARIA 209 which is dot-like, or transversely elongated, is the smallest, but the most important, for anatomical investigation has shown that this alone represents the vascular bundle of the leaf. The two lateral prints are vertically elongated, and are either straight or crescent- shaped, with the concavity directed inwards. These lateral marks are of the same nature as the parichnos of Lepidodendron. I m - mediately above the scar, and sometimes seated in a depression <r/A edge, is print, evidently represents the ligular pit (Fig. 88, /^). We thus see that, except for trifling j details, there is no difference in morpho- logy between the leaf- scars of Sigillaria and those of Lepido- dendron. When we come to the arrangement of the scars, we meet with considerable variations within the genus ; these variations have been used for the distinction of subgenera, which some authors have even erected into distinct genera. We shall see, however, that in the light of our present knowledge very little, if any, taxonomic value can be attached to these differences, though they are worth noting for descriptive purposes. H. Fig. 88.—Sigillaria Brardi (Leiodermaria type). Part of surface of stem, showing five leaf-scars. Ig, ligule ; v.b., print of vascular bundle; pa, parichnos. X *. After Weiss.. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.. Scott, Dukinfield Henry, 1854-1934. London, A. and C. Black
