CHAPTER XII 

 DIVISION 3. PTERIDOPHYTA : THE FERN PLANTS 



These are the highest of the cryptogams, a name which 

 was long since applied to the three divisions of plants pro- 

 ducing free spores, because their sexual reproduction was 

 believed to be hidden or obscure in contrast with that of the 

 phanerogams (the Flowering Plants or Spermatophytes), 

 where it seemed obvious. Though not wholly accurate in 

 fact, the word is retained for its convenience. Pteridophytes 

 are often called also vascular cryptogams, because they 

 alone of Cryptogams possess a vascular system. This, 

 however, they share with the next division, the Spermato- 

 phytes, with which they are sometimes combined as 

 vascular plants. The Pteridophytes and Bryophytes 

 together are often called archegoniat^e, because they pos- 

 sess in common, and exclusively, the distinctive archegonium. 



At first sight the Pteridophytes present a very heterogene- 

 ous aspect, for they include with the familiar Ferns the wholly 

 dissimilar little floating Water Ferns, the rush-like Horse- 

 tails, and the Club Mosses, which suggest true Mosses but 

 are coarser and creeping. Although the plant bodies are 

 so different, the reproduction shows features which unite 

 them all into one group. 



The Pteridophytes possess in common five important 

 features which mark them off from the Bryophytes. First, 

 their well-developed vascular system, containing true ducts 

 and sieve-tubes, has enabled them to grow greatly in height, 

 even to forming trees in tropical forests, while the Bryo- 

 phytes, now as probably in the past, reach hardly a foot above 

 ground. Not only the vascular system, but the other tis- 



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