162 



PTERIDOPHYTES 



and is composed of modified leaves or Sporophylls, bearing small 

 sacs or sporangia containing the spores. The spores have four 

 spiral rings which straighten out when dry and roll up when 

 wet and thus cause the spore to move over short distances. The 



Fig. 103. — Diagrammatic representation of the life history of the fern: a, prothallium; 

 b', antheridium; b", archegonium; c', sperm; c", ovum; d, oospore; e, prothallus and young fern; 

 f , mature fern showing under-ground stem, root and leaf bearing sori ; g, sporangium ; h, spores. 



life history of the horse tail is practically the same as that of 

 the true fern. 



Other Fern-like Plants. — The so-called club mosses or 

 ground pines, the selaginellas and the quillwort are groups of 

 small plants which have life histories very similar to that of the 

 true ferns. 



The greatest value of the ferns at the present time lies in 

 their great beauty for decorations of various kinds and we must 



