THE BRIAN OR DEVONIAN FORESTS. 



74 



trees, and the manner in which they anticipate those of 

 the true exogens of modern times, have been admirably 

 illustrated by Dr. Williamson, of Manchester. His 

 papers, it is true, refer to these plants as existing in the 

 Carboniferous age, but there is every reason to believe 

 that they were of the same character in the Erian. The 

 plan is the same with that now seen in the stems of exoge- 

 nous phaenogams, and which has long ceased to be used 

 in those of the Lycopods. In this way, however, large 

 and graceful lycopodiaceous trees were constructed in the 

 Erian period, and constituted the staple of its forests. 



The roots of these trees were equally remarkable with 

 their stems, and so dissimilar to any now existing that 

 botanists were long disposed to regard them as inde- 

 pendent plants rather than roots. They were similar in 

 general structure to the stems to which they belonged, 

 but are remarkable for branching in a very regular man- 

 ner by bifurcation like the stems above, and for the fact 

 that their long, cylindrical rootlets were arranged in a 

 spiral manner and distinctly articulated to the root after 

 the manner of leaves rather than of rootlets, and fitting 

 them for growing in homogeneous mud or vegetable 

 muck They are the so-called Stigmaria roots, which, 

 though found in the Erian and belonging to its lycopo- 

 diaceous plants, attained to far greater importance in the 

 Carboniferous period, where we shall meet with them again. 



There were different types of lycopodiaceous plants 

 in the Erian. In addition to humble Lycopods like those 

 of our modern woods and great Lepidodendra, which were 

 exaggerated Lycopods, there were thick-stemmed and less 

 graceful species with broad rhombic scars (Leptophleum), 

 and others with the leaf-scars in vertical rows {Sigillaria), 

 and others, again, with rounded leaf-scars, looking like 

 the marks on Stigmaria, and belonging to the genus 

 Cyclostigma. Thus some variety was given to the arbo- 

 real club-mosses of these early forests. (See Fig. 15.) 





