Plant Structures; A Second Book of Botany (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1900 Excerpt: ...spores are all alike, Lycopodium has the same homosporous-eusporangiate combination noted in Equisetales and in one of the groups of Filicales. 89. Selaginella, --This large genus contains the smaller, more delicate Club-mosses, often being called the "little Club-mosses." They are especially displayed in the trop Fig. 138. Selaginella, showing general spray-like habit, and dangling leafless stems which strike root (rhlzophores).--From "Plant Relations." ics, and are common in greenhouses as delicate, mossy, decorative plants (Fig. 138). In general the sporophylls are not different from the ordinary leaves (Fig. 139), but sometimes they are modified, though not so distinct as in. certain species of Lycopodium, The solitary sporangium appears in the axils (upper angles formed by the leaves with the stem) of the leaves and sporophylls, but arise from the stem instead of the Fk;. 139. Selaciinella Martenxii: A, branch bearing strobili; /?, a microsporophyll with a microsporangium, showing microspores through a rupture in the wall; C, a megasporophyll with a megasporangium; D, megaspores: K, microspores.Caldwell. tiyU with a leaf (Fig. 139). This is important as showing that sporangia may be produced by stems as well as by leaves, those being produced by leaves being called foliar, and those by stem cauline. The most important fact in connection with Selaginella, however, is that it is heterosporous. Megasporangia, each usually containing but four megaspores, are found in the axils of a few of the lower leaves of the strobilus, and more numerous microsporangia occur in the upper axils, containing very many microspores (Fig. 139). The character of the gametophytes of heterosporous Pteridophytes may be well illustrated by those of Selaginella. ...