CHARACTERS OF PTERIDOPHYTKS. 189 



irregular lobed body, sparingly furnished on its under sur- 

 face with small root-hairs." The antheridia arid archegonia 

 appear to be produced on the upper sur- 

 face, and these by their interaction, give 

 rise to the new plant which bears the 

 spores, just as in the Ferns and Horse- 

 tails ; so that again there is an alternation 

 of generations. 



335. It is a fact of great interest that 

 in some plants nearly related to the Club- 

 Mosses, two Id7ids of spores large and small are produced 

 in separate sporangia. The large ones develope prothallia 

 upon which archegonia are formed, and the smaller others 

 upon which antheridia appear. 



336. The three plants just considered, while evidently 

 differing in certain details of structure and in general 

 aspect, nevertheless have a number of characters in 

 common : 



1. They agree in their mode of reproduction, which is 



by spores, these bodies being quite unlike the SEEDS 

 with which we are now familiar, and which, you will 

 recollect, always contain the embryo of the neiv 

 plant. 



2. They all exhibit an alternation of generations. 



3. They all have true roots. 



4. The three tissue-systems the epidermal, the fibro- 



vascular, and the fundamental though not all 

 developed to so high a degree as in the Phanerogams, 

 still can be very clearly made out in 'both roots and 

 stems. The fibro-vascular bundles are always closed, 

 as in monocotyledons, and are, as a general rule, 

 concentric (299). 



Fig. 238. Leaf of Lycopodium bearing sporangium ; greatly magnified. 

 .'Thona(5.) 



