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CHAPTER V. 



Group III. 

 PTEBIDOPHYTA. 



This group, which is sometimes known as the group of the 

 Vascular Cryptogams, includes the Ferns, the Equisetums or 

 Horsetails, and the Lycopodinse or Club-mosses. They are 

 called Vascular Cryptogams, to indicate that their tissues con- 

 tain well-differentiated vascular structures, which we have seen 

 to be almost entirely unrepresented in the preceding two groups. 

 The life history embraces two phases, as in the case of the 

 Bryophyta, but the order of their greater prominence is reversed. 

 The gametophyte is small, cellular, and usually of very short 

 duration ; the sporophyte forms what is commonly called ' the 

 plant,' and may persist for many years. Ii shows considerable 

 morphological and histological differentiation. 



Comparing the group with that of the Bryophyta we note 

 especially the retrogression in size of the gametophyte, and the 

 great advance made by the sporophyte. Further, that the 

 sporophyte does not remiain all its life parasitic on the gameto- 

 phyte, but that it develops roots and leaves, and soon becomes 

 independent of the latter, which usually perishes as soon as 

 the sporophyte becomes well established. The latter generally 

 persists many years, producing its spores annually. 



In describing the forms which are included in the group, it 

 is weU to begin with the sporophyte on account of this predomi- 

 nance. 



It shows considerable morphological differentiation, possess- 

 ing, with few exceptions, root and shoot, the latter consisting of 

 stem and leaves. The stem is often of considerable size ; its 

 growth may be sub-aerial, but it frequently takes the form of a 

 rhizome. 



The leaves are of very various sizes ; in the fei-ns as a rule 

 they are large and compound ; in the club-mosses much smaller 

 and more numerous ; in the horsetaUs reduced to scales closely 



