36 THE PRESENT. 



of Endogens, whose increase takes place from within by a 

 coalescence of the footstalks of the old leaves, as in the 

 palm ; of Acrogens, or those that increase by shooting from 

 the top, as the ferns and horsetails, and whose stems are 

 thus generally thicker above than below ; and of Amphigens, 

 or those which grow by additions to the external margin, 

 and spread, as it were, on every side, as in the sea-weeds 

 and lichens. Founding in this way first, on the different 

 modes of reproduction ; second, on the aspect of the repro- 

 ducing organs; thirdly, on the primary development; and 

 fourthly, on the ultimate development of the plant the 

 botanist arrives at a scheme of classification which may be 

 briefly expressed as in the annexed tabulation. 



It is true, the palaeontologist cannot always avail himself 

 of the terms and classification of the botanist, as there occur 

 in the geological formations a number of forms that stand 

 intermediate between existing orders and families, and of 

 which we have now no living representatives. Still, these 

 forms never diverge so widely from any of the existing 

 families but that their affinities can be determined with 

 some degree of certainty ; and at all events, even where 

 family alliance fails, they can be readily ranked under the 

 wider categories of orders and sections. It is thus that the 

 subjoined scheme embraces alike the extant and extinct 

 the latter supplying the links that unite the whole into a 

 still more homogeneous and consistent system : 



