874 LIFE : OUTLINES OF GENERAL BIOLOGY 



In the Early Devonian Period, when the highest animals were 

 fishes, there was a terrestrial vegetation. This is illustrated by the 

 puzzling primitive Rhyniaceas found by Dr. Mackie in a fossilised 

 peat-bed at Rhynie in Aberdeenshire. Perhaps they linked the 

 moss-tribe (Bryophytes) to the fern-tribe (Pteridophytes) ; they 

 were in any case very simple and unique land plants. Later on, in 

 the LTpper Devonian, the land vegetation had made much progress, 

 for there were many ferns and club-mosses, besides graceful Spheno- 

 phylls which have no living representatives to-day. It was about that 

 time that Amphibians began to emerge, the distant ancestors of 

 our frogs and newts. Now it was during this eventful time that 

 there appeared the first plants with seeds; and they became 

 numerous in the next period, that of the Coal Measures. The pioneer 

 seed-bearers were for a long time regarded as ferns, to which they do 

 not seem to be closely related, and they often get the name of 

 seed-ferns or Pteridosperms. Perhaps a better name, though a 

 longer, is Cycadofilicales, which suggests that they show a combina- 

 tion of fern-like and Cycad-like features. There is no doubt that they 

 had seeds, though we have been told that investigators who have 

 made microscopic sections have never found an embryo inside the 

 fossil. These early seed-bearers, beginning in the Devonian, were 

 exuberant in the Carboniferous, and they were eventually accom- 

 panied by cycads, conifers, and maidenhair- trees, showing us that 

 we must correct or adjust the old description of the Carboniferous 

 as "the Age of Cr5rptogams". 



But while we are for the moment emphasising these primitive 

 "Cycad-Fern" seed-plants, we must still picture the dense damp 

 Carboniferous forests, whose debris formed the valued coal-measures 

 of many countries, as mainly cryptogamic. Thus there were, 

 besides ferns and tree-ferns, huge Lepidodendron club-moss-trees, 

 such a contrast to their modern representatives, like the "stag's 

 horn moss" on our moorland and the delicate Selaginellas in our 

 greenhouse. There were Horsetails, too, rising to a stature of a 

 hundred feet, such a contrast to our humble Equisetums by the 

 roadside, or in the wood and the marsh. Yet there are glimpses of 

 the distant aeons in some American everglades of to-day where the 

 horsetails far overtop the horse and his rider. We must not linger in 

 the Carboniferous forests, but we cannot but mention the prob- 

 ability that some of the delicate Sphenophylls — unfortunately not 

 included in the modern roll-call — were climbing plants, like so 

 many in the tropical forests of to-day, or like the bindweed in our 

 hedgerow jungles. 



The exuberance of flowerless plants in Carboniferous forests has 

 meant much to man, who has learned to use, for good and ill, the 

 stores of bottled sunshine in the coal ; but we are on a different line 

 of thought just now. Our question is: What led to the seed-plant. 



