. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. REPRODUCTION, VEGETABLE (VEGETABLE OVUM). 58. First period* — From the germination of the spore arises a tubular filament, which is converted directly, by successive divisions, into a simple riband-like frond, with a notch in its anterior margin, containing a young shoot. At whatever age the plant be ob- served, the actively growing portions are shoots which resemble the spore plant in form and structure, and it is at various points of the upper surface of these shoots that the reproductive organs are developed. 59. The
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. REPRODUCTION, VEGETABLE (VEGETABLE OVUM). 58. First period* — From the germination of the spore arises a tubular filament, which is converted directly, by successive divisions, into a simple riband-like frond, with a notch in its anterior margin, containing a young shoot. At whatever age the plant be ob- served, the actively growing portions are shoots which resemble the spore plant in form and structure, and it is at various points of the upper surface of these shoots that the reproductive organs are developed. 59. The development of the antheridia com- mences in the still very young shoot, by the separation "of a circular group of about sixteen of the superficial layer of cells from those of the tissue below it. There results a small lentil-shaped lacuna in the parenchyma, which Fig. £33 divides by a vertical septum, parallel to a plane touching the centre of its outer sur- face. This meets the perpendicular wall last formed at 45°, and divides the cell into an external tetrahedral, and an internal three-sided compartment. The latter divides twice by septa, which cross each other at right angles, so as to form a central group, which, as it rapidly enlarges, causes the four less actively growing cells by which it is sur- rounded to assume a tabular form. In its further development it is converted into a mass of very numerous and minute regularly- arranged tessellar cells, in each of which is found " a lentil-shaped vesicle which occupies the greater part of its ; Shortly before the antheridium arrives at maturity, the mem- brane of the cells disappears ; the vesicles float free, and there is now found rolled up in each, a spiral fibre of from 2\ to 3 coils, which is coloured yellow by iodine. The ripe antheridium presents the. general form and ap- pearance shown in fig. 156. The cellular mem- Fig. 156. Section of young shoot of Anthoceros levis, passing throug
Size: 1695px × 1475px
Photo credit: © Central Historic Books / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bo, booksubjectanatomy, booksubjectphysiology, booksubjectzoology
