. Our native ferns and their allies : with synoptical descriptions of the American Pteridophyta north of Mexico. Ferns. 32 Our Native Ferns CHAPTER IV GERMINATION OF FERN SPORES Alle Glieder bilden sich aus nach ew'gen Gesetzen, Und die seltenste Form bewahrt im Geheimniss das Urbild. —Goethe. 70. The germination of the fern spores usually takes place a considerable time after they are discharged from the sporangia, but in Osmunda which develops its fruit early in the season they commence their growth only a few days after dissemination. 71. Thalloid Phase. (Sex- ual Generation).—In germina- t
. Our native ferns and their allies : with synoptical descriptions of the American Pteridophyta north of Mexico. Ferns. 32 Our Native Ferns CHAPTER IV GERMINATION OF FERN SPORES Alle Glieder bilden sich aus nach ew'gen Gesetzen, Und die seltenste Form bewahrt im Geheimniss das Urbild. —Goethe. 70. The germination of the fern spores usually takes place a considerable time after they are discharged from the sporangia, but in Osmunda which develops its fruit early in the season they commence their growth only a few days after dissemination. 71. Thalloid Phase. (Sex- ual Generation).—In germina- tion the exospore splits along the side and the protruding en- dospore, sometimes with its di- visions already formed by septa or partitions, forms, not a fern, but a thalloid structure resem- bling a lichen or marchantia, called the prothallium. Differ- ent ferns vary in the method of forming this prothallium, some producing it immediately at the spore and others after the formation of a thread-like. Fig. 22-3. Prothallium of Pterin ser- nilata, Linn, f., showing two stages of growth. (After Moore.) growth known as the pro-embryo. The prothalHum is entirely composed of cellular tissue, and in the true ferns (Polypodiace^) is broadly cordate or reniform in shape, and bears large numbers of root-hairs from the under part of its posterior portion (Fig. 22-3.) The prothallium seldom exceeds one-tenth of an inch in length. On the under surface of the prothallium two sorts of organs are produced analagous to the stamens and pistils of the Phanerogamia, respectively known as antheridia and archegonia. The position of these organs on the prothallium varies in different sub-orders. 72. Antheridia.—These are small masses of tissue developed in the same manner as the root-hairs, consisting of a single layer of cells forming the wall and containing a number of spirally coiled threads usually with a number of cilia on their anterior. Please note that these images are extracted from sc
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