. Our native ferns and their allies [microform] : with synoptical descriptions of the American pteridophyta north of Mexico. Ferns; Fougères. FRUCTIFICATION IN FERNS. II of flowering plants. These spores are collected in little sacs known as sporangia or spore cases. The sporangia in the true ferns (POLYPODiACEiE) are collected in little clusters on the back of the frond, or are variously arranged in lines along the veins or around the margins (Fig. i). These clusters of spo- rangia are called sort, and may be naked, as in Potypodium, or provided with a special covering known as the indusiuniy
. Our native ferns and their allies [microform] : with synoptical descriptions of the American pteridophyta north of Mexico. Ferns; Fougères. FRUCTIFICATION IN FERNS. II of flowering plants. These spores are collected in little sacs known as sporangia or spore cases. The sporangia in the true ferns (POLYPODiACEiE) are collected in little clusters on the back of the frond, or are variously arranged in lines along the veins or around the margins (Fig. i). These clusters of spo- rangia are called sort, and may be naked, as in Potypodium, or provided with a special covering known as the indusiuniy as in Dryopttris (Fxf^.Z). The various forms of the sori and indusia serve as the basis for classifica- tion into genera and tribes, while each sub-order has its peculiar form of sporangia. 27. In the PoLYPODiACEiE the sporangia are more or less completely surrounded with a jointed vertical ring or annulus, and at maturity burst open transversely by the straightening of the annulus and discharge their copious spores (Fig. 2). The clusters of sporangia are said to be marginal, intramarginal, or dorsal, according as they have their position at the margin or more or less remote from it. They may be . ^ roundish, oblong, or linear in shape, or arranged dium vuiga't^i^^ in variously forking lines, or may even be spread J^res'^^wfiLch en' in a stratum over the entire under surface of the '"k*^- frond. They are called indusiate or non-indusiate according as they are covered or naked; and the indusia may be inferior (at- tached below the sorus), as in Woodsia (Fig. 9), or superior, as inDrjfopiertsiF')t or of various intermediate methods of at- tachment. 28< In the other families of Filicales the sporangia are variously arranged. In the Hymenophyllace^ or filmy ferns the flattened spo- rangia are sessile along a filiform receptacle, and are surrounded with a complete transverse annulus. At ma- turity they open vertically. Fica.—Sporen-. Please note that these images are
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