Archive image from page 319 of The cyclopædia of anatomy and. The cyclopædia of anatomy and physiology cyclopdiaofana05todd Year: 1859 244 REPRODUCTION, VEGETABLE (VEGETABLE OVUM). of which a structure is formed composed of is occupied by a large cell, which is enclosed a . series of cylindrical cells placed end to by a single layer of others, and supported end, The growing extremity of this body, the so-called suxpensor, penetrates the single layer of cells which separate it from the in- Fig. 178. ferior surface of the prothallium, and buries itself in the cushionlike mass. A new deve- l
Archive image from page 319 of The cyclopædia of anatomy and. The cyclopædia of anatomy and physiology cyclopdiaofana05todd Year: 1859 244 REPRODUCTION, VEGETABLE (VEGETABLE OVUM). of which a structure is formed composed of is occupied by a large cell, which is enclosed a . series of cylindrical cells placed end to by a single layer of others, and supported end, The growing extremity of this body, the so-called suxpensor, penetrates the single layer of cells which separate it from the in- Fig. 178. ferior surface of the prothallium, and buries itself in the cushionlike mass. A new deve- lopment now commences in the terminal /&& cell, which is divided by a succession of septa alternately in opposite directions. [[ U Fig. 176. Two germ plants of Selaginella Martensi, which have taken their origin from a sinyle macrospore, 5 diam. on a short pedicle. As it advances towards maturity, the spore-case consists of a capsule of three layers. Of these the external or epidermic, is composed of narrow prismatic cellules containing only a transparent fluid. The cells of the middle layer are tabular, and contain starch granules, while those most internal are narrow and somewhat columnar, with very delicate walls. Within this capsule is enclosed a central mass of larger cells, which exhibit central nuclei and granular contents. These, which are the parent cells of the spores, are at first intimately united, but afterwards lie loose in the cavity of the spore-case. Up to this point the development of all the sporangia is uniform. In those in which macrospores are to be produced (oophoridia), one of the parent cells, in no respect different from its fellows in struc- ture, continues to increase in size while they disappear. Its nucleus is soon replaced by four others, which arrange themselves, as in Eqnisetum, towards the four angles of a regular tetrahedron. Septa are afterwards formed, which divide the cell into four com- partments, in each of which a spore is de- veloped.
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