. Comparative anatomy of the vegetative organs of the phanerogams and ferns. Plant anatomy; Phanerogams; Ferns. VESSELS. l6j arranged: thus the narrow, closely-grouped transverse slits in the ladder-like oblique walls of the pitted vessels in the wood of the Betulacege, Ericaceae, of Corylus, Carpinus, Pteris aquilina; the round openings of the oblique walls of Ephedra arranged in 1-2-3 rows, &c. Rarely the slits are parallel to the longitudinal axis of the vessel: e. g. vessels of Hieracium vulgatum, Onopordon Acanthium, in which irregular reticulate openings also occur. In an Avicennia S
. Comparative anatomy of the vegetative organs of the phanerogams and ferns. Plant anatomy; Phanerogams; Ferns. VESSELS. l6j arranged: thus the narrow, closely-grouped transverse slits in the ladder-like oblique walls of the pitted vessels in the wood of the Betulacege, Ericaceae, of Corylus, Carpinus, Pteris aquilina; the round openings of the oblique walls of Ephedra arranged in 1-2-3 rows, &c. Rarely the slits are parallel to the longitudinal axis of the vessel: e. g. vessels of Hieracium vulgatum, Onopordon Acanthium, in which irregular reticulate openings also occur. In an Avicennia Sanio found the hori- zontal septum surrounded by a sharply-marked thickened margin, and the whole remaining surface covered with many irregular, round or slit-shaped, bordered openings^. There is no constant relation between the form of thickening of the lateral wall and the form of perforation. Nevertheless most vessels with fibrous- thickening have round openings, and very many vessels with bordered pits have ladder-like perforations. In pitted vessels, however, simple openings are also frequent, and Sanio found ladder-like perforations in the spiral vessels of species of Casuarina, Olea europaea, and Vilis. In thin-walled vessels—such as most of those with fibrous thickening, and thin-walled pitted vessels, e. g. in the wood of Betulaceae and of Tilia—the margin of the opening of the septum is smooth and thin, corresponding to the margin of very flat, not bor- dered pits. In thick-walled vessels it is thicker, and has the structure of a pair of corresponding bordered pits opened by disappearance of the limiting lamella, and with but small difference of width between the pit- cavity and the wide orifice of the pit: it consists therefore of two acutely-diverging lamellae. In many vessels this structure as of a bor- dered pit is extremely striking, e. g. in the large solitary openings of the pitted vessels in the wood of Nerium, Fraxinus, Convolvulus Cneorum (Fig. 64), Piru
Size: 1414px × 1767px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecad, booksubjectplantanatomy, bookyear1884
