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revised in the light of more trustworthy evidence. 

 It was shown in the later part of the nineteenth 

 centur}^ by the late Professor Williamson of Man- 

 chester, whose researches into the plants of the 

 Coal age shed a flood of light on the ancestry and 

 inter-relationship of many existing plants, that some 

 of the fern-like leaves which have long been familiar 

 to those who search among the shales of the refuse 

 heaps of collieries, were borne on stems differing in 

 anatomical features from those of any known fern. 

 The investigation of the structure of the leaves and 

 their supporting stems led to the recognition of 

 certain extinct genera of Palaeozoic plants of excep- 

 tional interest, to which the term generalised type is 

 aptly applied. Associated with anatomical and other 

 characters such as we now regard as the attributes 

 of ferns, these plants exhibit other features not met 

 with in modern ferns but characteristic of a group of 

 seed-bearing plants known as the Cycads. Recent 

 research has revealed the existence of several such 

 generalised types which, by their combination of 

 characters now met with in distinct sub-divisions 

 of the plant-kingdom, clearly indicate the derivation 

 of Ferns, and Cycads as we know them to-day, from 

 a common stock. It was in the first instance by 

 means of anatomical evidence — obtained by the 

 microscopical examination of sections of petrified 

 fragments of stems and leaves — that the generalised 



