. Our native ferns and how to study them; with synoptical descriptions of the North American species. Ferns. Germination. 37 CHAPTER IV. GERMINATION OF FERN SPORES. Alle Glieder bilden Bich aua nach ew'gen Gesetzen, Und die seltenste Form bewahrt im Geheimniss das Urbild. —Goethe. 67. 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. 68. The Sexual Generation ( Oophore ). — In germination the exospore
. Our native ferns and how to study them; with synoptical descriptions of the North American species. Ferns. Germination. 37 CHAPTER IV. GERMINATION OF FERN SPORES. Alle Glieder bilden Bich aua nach ew'gen Gesetzen, Und die seltenste Form bewahrt im Geheimniss das Urbild. —Goethe. 67. 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. 68. The Sexual Generation ( Oophore ). — In germination the exospore splits along the side and the protruding endo- spore, sometimes with its divi- sions already formed by septa or partitions, forms, not a fern, but a thalloid structure resem- bling a lichen or marchantia, called the prothallium. Diflfer- ent ferns vary in the method of forming this prothallium, some producing it immediately ^.^ ,^^ TrothMinm of Ptens ser^aia, at the spore and others after Linn, f., ahowing two slagee of growth. the formation of a thread-like (After Moore). growth known as the pro-embryo. The'prothallium is entirely composed of cellular tissue, and in the true ferns (PolypodiacevE) is broadly cordate or reniform in shape, and bears large numbers of root-hairs from the under part of its posterior portion, (Fig. 23-4.) The prothallium seldom exceeds one-tenth of an inch in length. On the under surface of the prothallium two sorts of organs are produced analogous to the stamens and pistils of the Phanerogamia, respectively known as antheridia and arche- gonia. The position of these organs on the prothallium varies in different sub-orders. 6g. 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 coils. At maturity the antheridium swells by the absorption of. Please not
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