. La structure et le développement de mousses et de fougères (Archegoniatae). Certains points d'Leitgebs les figures de Fontinalis. Fig. 98, un Ashows exactement section longitudinale médiane par un stronggrowing point. Par rapport aux chiffres de l'Leitgebs cellis apicale beaucoup plus profond que dans fontinalis, et par voie de conséquence, la young-segments les plus près de la verticale. Ici, comme dans la sphaigne, l'firstwall dans le segment des jeunes le divise en une et une outercell, à partir de laquelle seules sont formés le VI. Les BRYALES 191 appendices de la tige. Les cellules internes des segments byrepeated un longitudinal

• Contributeur: The Reading Room / Alamy Banque D'Images
• ID de l’image: 2AFKFWR
• Taille du fichier: 7,1 MB (279,4 KB Téléchargement compressé)
• Autorisations: Modèle - non | Propriété - non
• Dimensions: 1764 x 1416 px | 29,9 x 24 cm | 11,8 x 9,4 inches | 150dpi

Informations supplémentaires

Cette image appartient au domaine public, ce qui signifie que le droit d’auteur a expiré ou que le titulaire du droit d’auteur a renoncé à ses droits. Les frais facturés par Alamy couvrent l’accès à la copie haute résolution de l’image.

Cette image peut avoir des imperfections car il s’agit d’une image historique ou de reportage.

. The structure and development of mosses and ferns (Archegoniatae). some points from Leitgebs figures of Fontinalis. Fig. 98, Ashows an exactly median longitudinal section through a stronggrowing point. Compared with Leitgebs figures the apical cellis much deeper than in Fontinalis, and in consequence the young-segments more nearly vertical. Here, as in Sphagnum, the firstwall in the young segment divides it into an inner and an outercell, from the latter of which alone are formed the lateral VI. THE BRYALES 191 appendages of the stem. The inner cells of the segments byrepeated longitudinal and transverse divisions form all the tis-sues of the axis. The second division wall in the segment, likethat in Sphagnum, is at right angles to the first, but in Ambly-stcgmm it extends the whole breadth of the segment. By thisdivision the outer of the two primary cells of the segment isdivided into an upper cell, from which the leaf develops, and alower one from which the outer part of the stem and the burlsare formed. The leaves grow from a two-sided apical cell. Fig. 98.—Amblystegium riparium, var. fluitans. A, IMedian longitudinal section of astrong shoot; x, apical cell; x, initial of a lateral branch, X250; B, transversesection through the apex, X250; C, similar section through a young branch, Xsoo* (Fig. 99), as indeed they seem to do in all Mosses, and thedivisions proceed w^ith great rapidity and the young leavesquickly grow beyond and surround the growing point. InAmblystegiiun, as in all the typical Bryalcs, the leaf has a well-developed midrib. The formation of this begins while the leafis very young and proceeds from the base. In the middle rowof cells (Fig. 99, C), a w^all first arises parallel to the surfaceof the leaf, and this is follow^ed by a wall in the cell on the lowerside of the leaf (Fig. 99, D). By further divisions in all the 192 MOSSES AND FERNS CHAP. cells of this central strand the broad midrib found in the matureleaf is developed. In Amhlystegiwn

Recherche dans la banque de photos par tags

• bookcentury1900
• bookdecade1910