. A textbook of botany for colleges and universities ... Botany. I2& MORPHOLOGY 270, 271, 272). The outer cells are the primary wall cells, which by subsequent divisions give rise to a sporangium wall of at least three layers of cells. The inner cells are the primary sporogenous cells, which by subsequent divisions give rise to a considerable mass of sporogenous tissue (fig. 273). This method of sporangium formation, by which the inner cells, following periclinal division of the superficial initials, give rise to the sporogenous tissue, is called the eusporangiate method, and plants exhibi
. A textbook of botany for colleges and universities ... Botany. I2& MORPHOLOGY 270, 271, 272). The outer cells are the primary wall cells, which by subsequent divisions give rise to a sporangium wall of at least three layers of cells. The inner cells are the primary sporogenous cells, which by subsequent divisions give rise to a considerable mass of sporogenous tissue (fig. 273). This method of sporangium formation, by which the inner cells, following periclinal division of the superficial initials, give rise to the sporogenous tissue, is called the eusporangiate method, and plants exhibiting it are often spoken of as eusporangiates. All vascular. Figs. 271——Sporangium of Lycopodium: 271, 272, view of young sporangium in different planes, showing primary wall layer, primary sporogenous tissue (shaded), and the underlying subarchesporial pad; 273, section showing further development of sporogenous tissue; 274, older sporangium, showing stalldike subarchesporial pad, three wall layers, the innermost of which is the tapetum (shaded), and the rounded off and separated spore mother cells. — After Bower. plants are eusporangiates except the modern ferns, whose peculiar method of sporangium formation will be described later. The sporogenous tissue is invested by a special nutritive layer known as the tapetum or tapetal layer (fig. 274). In Lycopodium the outer portion of the tapetal layer is composed of the innermost wall layer, and the inner portion of the sterile tissue contiguous to the sporogenous tissue. The tapetum, therefore, is simply the layer of sterile cells abutting against the sporogenous tissue, which have been transformed into feeding cells. This function gives to the layer a very characteristic appearance, making it quite distinct from the sterile tissue outside. 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
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