. Our native ferns and their allies [microform] : with synoptical descriptions of the American Pteridophyta north of Mexico . Ferns; Ferns; Pteridophyta; Fougères; ; . lES. FRUCTIFICATION IX FERNS. II s of great ore cspeci- 5, like most ising from oilier vein. , ill others nastomose 'o/ce. This ng a single he margin, inn areola; istinct and In case icted light, etwoen the essary. A IS. ing plants lere is a )ro'Auction, nale organs zed by the le stamens, :he embryo riie Ferns, roducc no ;ed ovules, w ferns are unlike that. of flowering plants. These spores are collected in little sacs known a
. Our native ferns and their allies [microform] : with synoptical descriptions of the American Pteridophyta north of Mexico . Ferns; Ferns; Pteridophyta; Fougères; ; . lES. FRUCTIFICATION IX FERNS. II s of great ore cspeci- 5, like most ising from oilier vein. , ill others nastomose 'o/ce. This ng a single he margin, inn areola; istinct and In case icted light, etwoen the essary. A IS. ing plants lere is a )ro'Auction, nale organs zed by the le stamens, :he embryo riie Ferns, roducc no ;ed ovules, w ferns are unlike that. of flowering plants. These spores are collected in little sacs known as upora/^i^'-m or spore cases. The s[)oraiigia in the true ferns (PoLYP()iJiACl!;.K) are ccjllected in little clusters on tin; back of the frond, or are variously arranged in lines along the veins or around the margins (I'*ig. i), These clusters of spo rangia are called sor/, and may be naked, as in Polypoiiium, or provided with a special covering known as the indusium^ as in Aspiilinin (Fig. 8). The various forms of the sori and iiulusia serve as the basis for classifica- tion into genera and tribes, while each sub-order has its peculiar form of sporangia. 27. In the Polyi'odiacivE the sporangia are more or less completely surrounded with a jointed vertical ring or anmilus, 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 it. They may be .âSporan- roundish, oblong, or linear in shape, or arranged ^'hnn TuJireAZ hi variously forking lines, or even be spread spores!"*^M^Lchen'^ in a stratum over the entire under surface of the ''"'f''*^^. 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 IVoodsta (Fig. 9), or superior, as
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Keywords: ., bookcentury1800, bookdecade1880, bookpu, booksubject, bookyear1888
