. L'anatomie développementale de l'Isoetes. L'Isoetes, la botanique. 16 L'AFFECTATION DE Anatomie d'IsOCteS de la feuille et la partie de la base des feuilles de revêtement qui s'affiche dans la section (fig. 4). Aucune distinction ne peut être faite entre les cellules qui vont donner naissance à l'apex de la tige et ceux qui fourniront le deuxième primordium foliaire. La Motte (1937) a émis l'hypothèse que l'axe de la tige rudimentaire est parallèle à l'axe de la première feuille, parce que la deuxième feuille émerge parallèlement à la première feuille. J'ai redessiné l'une de ses figures comme figure 3.. Ligule gaine de la première feuille, racine première Figs. 3

• Contributeur: Paul Fearn / Alamy Banque D'Images
• ID de l’image: RCW9M3
• Taille du fichier: 7,2 MB (269,2 KB Téléchargement compressé)
• Autorisations: Modèle - non | Propriété - non
• Dimensions: 1948 x 1283 px | 33 x 21,7 cm | 13 x 8,6 inches | 150dpi

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. The developmental anatomy of Isoetes. Isoetes; Botany. 16 THE DEVELOPMENTAL ANATOMY OF IsOCteS of the leaf and the portion of the sheathing leaf base that appears in the section (fig. 4). No distinction can be made between the cells that will give rise to the shoot apex and those that will furnish the second leaf primordium. La Motte (1937) has speculated that the axis of the rudimentary shoot is parallel to the axis of the first leaf because the second leaf emerges parallel to the first leaf. I have redrawn one of his figures as figure 3.. Ligule Sheath of the First Leaf First Root Figs. 3 and 4. Sagittal sections of sporophytes in the first plastochron. Fig. 3. The sheath of the first leaf has not yet developed. Taken from La Motte (1937, fig. 13). Magnification not known. Fig. 4. /. howellii at a stage older than the sporophyte in figure 3. The sheath of the first leaf is partially de- veloped. The ligule mother cell has divided transversely, initiating the develop- ment of the multicellular ligule of the first leaf. X 390. Although the axis of the shoot is difficult to locate when the sporeling has only one leaf, it is not likely that this axis is parallel to that of the first leaf in the early stages of development (fig. 3). However, as the second plastochron is approached, growth in the region opposite the insertion of the first leaf tends to reorient the superficial cells so that the axis of the shoot and the first leaf are more closely aligned than they were initially (fig. 4). With the advent of the second primordium, cer- tain cells of the shoot tip assume characteristics that set them apart from the rest of the meristematic tissue. These cells mark the center of the shoot apex and are the apical initials of the shoot. These initials enlarge and stain less deeply or with a slightly different hue after the sections have been stained with progressive hematoxylin-safranine-fast. Please note that these images are extracted from scanned page images that may h

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