122 STUDY OF COMMON PLANTS. 



studied groups of plants. They are of special interest as 

 representatives of the higher flowerless plants, the vascular 

 cryptogams, since they share with them certain develop- 

 mental features that are wanting or are imperfectly seen 

 in phanerogams. The alternation of generations is far more 

 easily recognized here than in flowering plants, since both 

 generations are characterized by structures of considerable 

 size. The oophyte, or sexual generation, presents us with 

 the prothallium, which is a relatively conspicuous, leaf-like 

 body, bearing archegonia and antheridia, structures that do 

 not occur in the same form in phanerogams. 1 The system- 

 atic literature is extended and rather expensive. Eaton's 

 Ferns of North America is the best for this country, and 

 the works of Hooker and Baker give the most help on 

 foreign species ; but with Gray's Manual or Underwood's 

 little book, the student will be able to identify without 

 difficulty the ferns indigenous to the region where he lives, 

 and this is suggested to him as an interesting and instruc- 

 tive piece of systematic work. 



1 On the homologies of these organs as they exist in higher plants cf . 

 Bennett and Murray, Cryptogamic Botany, p. 11 et seq. ; Goebel, Out- 

 lines of Classification and Special Morphology ; Macraillan, Metaspermaz 

 of the Minnesota Valley, and recent periodical literature. 



