CONCLUSION 237 



theory of Evolution in affording abundant evi- 

 dence that at all known periods, adaptation, 

 under the existing conditions, has always been as 

 perfect as it is now. 



In limiting this little book to the subject 

 of the evolution of the higher plants we have 

 had the advantage of dealing with those groups 

 for which historical evidence, from the fossil 

 record, is available. As regards the rest of the 

 vegetable kingdom the Bryophytes, the Algse 

 and the Fungi there is as yet comparatively 

 little help from fossils; for the most part the 

 evolutionist has here to rely on the comparison 

 of living forms. Even in the more favourable 

 field which we have chosen the work is difficult 

 enough, and its results still tentative and pro- 

 visional. 



The whole problem of Descent is in fact extra- 

 ordinarily complex, and we are now only at the 

 beginning of the investigation. Evolution, during 

 the periods to which our records extend, proves 

 to have been by no means a regular advance 

 from the simple to the complex. Very often, 

 indeed, the reverse has been the case. The Horse- 

 tails and Club-mosses of the present day are very 

 much simpler than those of the Palaeozoic period; 

 the Cycads are now much less highly organised 

 than their Mesozoic relations. What the record 

 really shows is a succession of dominant groups, 



