CONCLUSION 301 



the Vascular Cryptogams. The latter, as at present 

 existing, form three quite distinct stocks, Horsetails, 

 Ferns, and Club Mosses, but in none of the three is there 

 the least evidence for any near relationship to the Bryo- 

 phytes. The sexual generation presents little difficulty ; 

 for instance, the thallus of a Pellia may well be compared 

 with the prothallus of a Fern. It is the sporophyte 

 which is so different in the two classes. Speaking broadly, 

 the asexual generation in the Bryophyta is always a 

 fruit, while in Vascular Cryptogams it is always a plant. 

 Nothing really approaching an intermediate form between 

 the two kinds of sporophyte has ever been discovered, 

 either among recent or fossil plants. 



Evidently these two great series the Bryophyta and 

 the Pteridophyta diverged very far back indeed. There 

 is no reason to suppose thafc the sporogoniuni of a Moss or 

 a Liverwort ever became modified into the asexual plant 

 of a Fern, Horsetail, or Lycopod. The two forms of 

 sporophytes have probably always been different from 

 the first origin of Archegoniatse onwards. There is direct 

 geological proof of the enormous antiquity of the Vascular 

 Cryptogams, which, together with certain Gynmosperrns, 

 were well developed even in the Devonian period ; their 

 origin is completely lost in the mists of palaeozoic anti- 

 quity, and at present we are entirely without any facts 

 which can throw light on the problem. The Bryophyta 

 may also have been an ancient group, but at present 

 there is little or nothing to show it. 



The Pteridophyta are much more highly organised 

 than any of the previous groups ; their advance is 

 entirely confined to the asexual generation, for the 

 oophyte remains throughout at a very low level (below 

 that of the simplest Bryophyta), and indeed degenerates 

 as we reach the higher forms, No doubt the aquatic 



