CHAPTER XVII 

 PTERIDOPHYTES (FERN PLANTS) 



General Discussion. — Ferns are much larger plants than 

 Bryophytes and consequently are much better known by the 

 general public. In the woods Ferns are common and often they 

 can be found in the fields. On account of their large, attractive, 

 feather-like leaves, they are common house plants and are ex- 

 tensively grown in greenhouses. Most Ferns require a moist or 

 shady region, but some are able to grow in dry situations. 



In studying the different layers of rock which form the earth's 

 crust, many Pteridophytes are found preserved. In the layer 

 of rock from which coal is obtained, Pteridophyte fossils are very 

 abundant. These fossils show that Pteridophytes were at one 

 time much more abundant than now. Some of these ancient 

 forms were like trees in size and resembled Seed Plants more than 

 any of the present forms do. Although the forms that made 

 most advancement toward Seed Plants have long been extinct, 

 the forms which now exist show us some of the lines along which 

 progress was made. 



In beginning the study of Pteridophytes, one should have in 

 mind the features contributed by the Bryophytes, because the 

 Pteridophytes are supposed to have come from forms like the 

 Bryophytes, although we are not able to connect them up with 

 any of the existing forms of Bryophytes. From forms like the 

 Bryophytes, the Pteridophytes inherited the land-habit. Thej^ 

 not only inherited those features which enable plants to live, 

 work, and reproduce in the air, but they have improved upon 

 these features, so that in general they are better fitted to li«ve on 

 land than most of the Bryophytes. They have the alternation 

 of generation which the Bryophytes so firmly established and 

 have carried the sterilization of sporogenous tissue so far that the 

 sporophyte is a massive and well differentiated plant body. 

 Probably, instead of speaking of it as sterilization of sporogenous 

 tissue, it would be clearer to say that the fertilized egg now pro- 



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