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 



