28 HOW TO KNOW THE FERNS 



a very important past. Although they are few 

 in number, as far as the species are concerned, 

 they still retain many striking characteristics. 

 Without a doubt the Palaeozoic Horsetails grew 

 into giant plants, sending out branches and 

 developing trunks which in some ways are 

 comparable to those possessed by our trees at 

 the present time. These great stems seem to 

 have arisen from rhizomes which travelled 

 about in the mud of the coal jungles. It is usual 

 to refer to these Palaeozoic Horsetails as Cala- 

 mites, owing to the fact that they were origin- 

 ally supposed to bear a resemblance to a reed 

 (Calamus). In the later rocks, such as those 

 which belong to the Jurassic and Triassic 

 periods, occur the Equisetites, plants which 

 were still of great size, but already in some 

 respects showing signs of that decline which has 

 culminated at the present day in the little 

 group of plants which, were it not for a certain 

 robustness of growth, would find it hard to 

 maintain their position at all. 



To complete our brief survey of the Vascular 

 Cryptogams it is now necessary that we should 

 review the position of these plants at the 

 present time. Of course in number the Ferns 

 are enormously in advance of all the other 

 plants put together. In the whole world, 

 there are not ,far short of seventy distinct 

 genera, which include anything between three 

 and four thousand species. The Ferns of the 

 United Kingdom number not far short of fifty, 

 and there are certain variations from the type 

 which some folk are tempted to include as 

 species. For some reasons which we cannot 

 well understand, the Ferns alone amongst the 

 Vascular Cryptogams have been able to hold 

 their own in the world. It is probable that 



