FOSSIL VASCULAR CRYPTOGAMS 



119 



(Daws.), from the Devonian and Carboniferous formations of Scotland 

 and North iVmerica, should also be included here. 



The only fossils that can be referred with any degree of certainty to 

 the Isoeteae are those comprised in the genus Iso'ctites (Schmp.), from the 

 Miocene, which is scarcely distinguishable from existing Isoetes. More 

 doubt rests on the true place of Solenites (L. and H.), from the Jurassic, 

 which has been referred with equal probability to Gymnosperms. 



Of fossil Psilotese the remains are few and uncertain. To this family 

 has been referred Fsilophyton (Daws.) ; but the fructification is very 



Fig. 91, — Bases of stem oi Sigillaria, with Stigviaria roots attached. (After Solms-Laubach. 



aberrant from the existing Psiloteae, consisting of a pair of pod-like 

 capsules at the end of special branches. 



Fossil Filices. 



The remains of ferns — or more commonly the impressions of the 

 leaves — are found in all fossiliferous strata from the Devonian on- 

 wards. Great difficulty is presented in the classification of fossil ferns 

 by the small fragments in which they are usually found, anything like 

 an entire plant, or even a number of fronds attached to an aerial stem 



