100 



ELEMENTARY STUDIES IN BOTANY 



great exposure to drying out is avoided, and fertilization is 



assured. 



When the fertilized egg in the archegonium germinates, 



it produces the large, 

 independent sporo- 

 phyte which is recog- 

 nized as " the fern " 

 (Fig. 78, B). 



It may have been 

 difficult for some to 

 think of the spore- 

 case of a liverwort or 

 a moss as being an 

 individual distinct 

 from the green plant 

 that bears it ; but 

 when in the Ferns 

 these two individuals 

 become entirely in- 

 dependent of one an- 

 other, the difficulty 

 disappears. 



60. The great 

 groups of Pterido- 

 phytes. The Pteri- 

 dophytes are very an- 



FIG. 81. Equisetum: showing the jointed and fluted cient plants for their 

 stem, the sheath of minute leaves at each joint, 



strobili in various stages of development, and history has been 

 some young branches. -, -, -, ,-, 



traced back to the 



time when coal was formed, and even before that time. 

 Their remains are found in the rocks, and this record of 

 their existence has shown not only that they were very 

 abundant, but . also that they were different from the 

 Pteridophytes that are living to-day. A number of great 

 groups lived and flourished and then disappeared, but they 



