. Practical botany. Botany. 306 PEACTICAL BOTANY. Fig. 252. Diagram of part of a seed cone of a pine, with ovules in normal position S, sporophylls, or leaf-like parts of the cone; 0, ovule (megasporangium); /, the covering of the ovule, called the integument; FG, the female gametophyte,whichbearsthearchegoniumyl,in which the egg is formed ; Ft, pollen tubes from pollen grains which lie upon the tip of the ovule depends. All sorts of useful and ornamental manufactured prod- ucts depend upon these timbers, and it is not easy to overestimate their value to mankind. 283. Asexual reproduction. Two
. Practical botany. Botany. 306 PEACTICAL BOTANY. Fig. 252. Diagram of part of a seed cone of a pine, with ovules in normal position S, sporophylls, or leaf-like parts of the cone; 0, ovule (megasporangium); /, the covering of the ovule, called the integument; FG, the female gametophyte,whichbearsthearchegoniumyl,in which the egg is formed ; Ft, pollen tubes from pollen grains which lie upon the tip of the ovule depends. All sorts of useful and ornamental manufactured prod- ucts depend upon these timbers, and it is not easy to overestimate their value to mankind. 283. Asexual reproduction. Two kinds of cones are borne upon a pine plant. One is the seed cone (Fig. 251) and the other is the staminate cone. An examination of a young seed cone will at once show structures somewhat sim- ilar to those of Lycopodium and Selaginella. The cone is composed of leaf-like structures, on the up- per sides of which ovules (megasporangia) (Fig. 252) are borne. In the ovules large cells, the megaspores, are formed, but one in each mega- sporangium. The spore does not escape from this megasporangium. Before relationships be- tween spermatophytes and pteridophytes were known, the megasporan- gium was always called an ovule, a name which is still largely used. The staminate cones bear the microsporo- phylls or stamens (Fig. 253), upon which are. 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 Bergen, Joseph Y. (Joseph Young), 1851-1917; Caldwell, Otis William, 1869- joint author. Boston, New York [etc. ] Ginn and company
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