. La botanique, avec les applications agricoles. La botanique. 196 Les faisceaux vasculaires des tiges de toutes les dicotylédones sont très sim- ilar à ceux de monocotylédones dans la structure et la fonction des vaisseaux conducteurs, mais diffèrent essentiellement d'avoir cambium. {Fig. 174.) Le tissu conducteur du xylème se compose principalement de spirale, annulaire, dénoyautées, et les navires scalariformes-cette dernière étant ainsi nommé parce que les zones épaissies, séparés par des zones telles que tableaux, sont organisées, l'une au-dessus de l'autre, comme pour ressembler à la ronde d'une échelle. Comme dans les monocotylédones, les vaisseaux du xylème, probablement aidé par les pare

• Contributeur: The Book Worm / Alamy Banque D'Images
• ID de l’image: RDTG9X
• Taille du fichier: 7,2 MB (413,6 KB Téléchargement compressé)
• Autorisations: Modèle - non | Propriété - non
• Dimensions: 1683 x 1485 px | 28,5 x 25,1 cm | 11,2 x 9,9 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.

. Botany, with agricultural applications. Botany. 196 STEMS The vascular bundles of all Dicotyledons are very sim- ilar to those of Monocotyledons in structure and function of conductive vessels, but differ essentially in having cambium. {Fig. 174.) The conductive tissue of the xylem consists chiefly of annular, spiral, pitted, and scalariform vessels—the latter being so named because the thickened areas, separated by sUt-like thin areas, are so arranged, one above another, as to resemble the rounds of a ladder. As in Monocotyledons, the xylem vessels, probably assisted by the neighboring parenchyma cells, are the passage ways through which the water and dissolved substances absorbed by the roots are distributed throughout the shoot. In addition to sieve tubes and companion. Fig. 175. — Cross section of a Flax stem, o, epidermis; d, bast fibers; c, cambium; p, phloem; x, xylem, h, pith. Enlarged. cells, the phloem of Dicotyledons generally contains many thin- waUed parenchyma cells, which serve in conducting the carbohy- drates and also as storage places for proteins. The sieve tubes and companion cells conduct the proteins and a part of the carbo- hydrates. The bast fibers, which commonly occur in connection with the phloem of all Dicotyledons, are tough flexible strands adapted to afford strength. In fiber plants, such as Flax and Hemp, the bast fibers are well developed and their importance in the manufacture of fabrics, as the manufacture of linen from Flax, is well known. (Fig. 175.) In contrast to the stems of Monocotyledons, the stems of Di- cotyledons and Gymnosperms have as their distinctive features the circular arrangement of vascular bundles and the presence. 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.. Martin, John N. (John Nathan), b. 1875. New York, John Wiley & sons, in

Recherche dans la banque de photos par tags

• bookcentury1900
• bookdecade1920
• booksubjectbotany
• bookyear1920