CHAPTER 16 



THE ANCIENT FERNS 



We have almost reached the end of this inquiry, and now it only remains to supplement 

 the account of the modern ferns given earUer in the book by adding some facts for the 

 ancient ones, choosing, as before, those groups with British representatives. In this case 

 there are three. Of the Eusporangiatae, thought to be the most ancient of all the 

 living ferns by Bower, we have the Ophioglossaceae, represented by the Adder's Tongue 

 {Ophioglossum) and the Moonwort {Botrychium). Of the Osmundaceae, placed by Bower 

 on the border between the Eusporangiatae and the more modern Leptosporangiatae, we 

 have Osmunda, and as an example of a Leptosporangiate group more primitive than the 

 Polypodiaceae we have the Hymenophyllaceae or Filmy Ferns, of which there are three 

 British representatives distributed among the two * genera which it contains, namely, 

 Trichomanes and Hymenophyllum. Taking these groups in the order mentioned we may 

 start with the Ophioglossaceae. 



Bower's reasons for regarding the Eusporangiatae, represented in Britain by Ophio- 

 glossum and Botrychium, as the most ancient of all living ferns are purely morphological 

 and depend on the fact that in the relatively massive construction of all parts of the 

 plant, especially of the sporangia and sex organs, these genera contrast strongly with 

 the undoubtedly modern Leptosporangiate ferns in features which Bower interprets as 

 primitive. Direct fossil record of these genera is wholly lacking, but granted the correct- 

 ness of the reasoning, which there seems no reason to doubt, it is certainly easier to derive 

 the living genera in imagination from certain extinct groups of the Carboniferous Period 

 known as the Coenopterideae than from any living ferns. 



The Eusporangiatae in the world as a whole are commonly subdivided into two main 

 groups, the Ophioglossaceae and the Marattiaceae, the latter consisting of a few genera 

 of archaic tree ferns, all of which are tropical, and for this reason excluded from this 

 survey at its present stage. The Ophioglossaceae contain only three genera, Ophio- 

 glossum, Botrychium and the tropical Helminthostachys, and therefore only the last will be 



excluded. 



The British species of Ophioglossum are two, 0. vulgatum L., the Common Adder's 

 Tongue, widely spread over the whole country in moist pastures and probably more 

 abundant, because of its inconspicuousness, than is generally supposed, and 0. lusitani- 

 cum L., a much smaller Mediterranean species with a well-known British locahty on the 

 island of Guernsey. Material of both these species has been available to me, and for con- 

 venience 0. lusitanicum will be taken first. 



The appearance of this httle plant at the end of its vegetative season (late April in 

 Guernsey) may be seen in Fig. 2610. It is a tiny fern forming a dense, close sward in 

 which some characteristic litde bulbous Monocotyledons, notably Scilla verna and 



* It should perhaps be noted here that Copeland (1947) replaces this simple classification of the 

 Hymenophyllaceae by no less than thirty genera, most of which are confined to the southern hemisphere. 



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