THE PTERIDOPHYTES 



285 



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264. The fern plant : gametophyte and sporophyte. Each 

 generation of the fern produces chlorophyll and can manufac- 

 ture its own food material. In a sense each is an independent 

 plant, but the gametophyte is too delicate to undergo severe 

 climatic conditions. It resembles some of the liverworts, but 

 its sexual reproductive structures are different. The embryo 

 sporophyte that 

 begins to grow 

 within the game- 

 tophyte is com- 

 plex, consisting 

 of foot, primary 

 root, stem, and 

 leaf, though but 

 two of these per- 

 sist in the adult 

 sporophyte. 



This embryo 

 begins its life 

 entirely inside 

 of the gameto- 

 phyte, but soon 

 emerges and be- 

 comes a sporo- 

 phyte plantlet. 



It should also be noted that in ferns there is a great reduc- 

 tion in the number of sperms produced in an antheridium as 

 compared with bryophytes, but each sperm is more complex. 

 Reduction in number seems to be balanced by the increased 

 efficiency of those that are formed. 



The sporophyte is the prominent fern plant and the chief 

 chlorophyll-working generation. It introduces new sporophyte 

 structures and habits, supporting and conducting tissues, and 

 the upright habit. This condition was forecasted in the sporo- 

 phyte of Anthoceros, but fern sporophytes are very much more 

 complex than those of Anthoceros. Though many asexual 



FIG. 237. A fern arcliegonium 



In the neck are the neck-canal cells, and at the base of the 

 neck is the egg. Greatly magnified 



