FOSSIL PLANTS. 



363 



its apparent, though more distant representative, in Chon- 

 dritis, a Lower Silurian alga, of which there seems to 

 exist at least three species. The fucoids, or kelp- 

 weeds, appear to have also 

 their representatives in such 

 plants as Fucoides gracilis, 

 of the Lower Silurians of 

 the Malverns ; in short, the 

 Thcdlogens of the first ages 

 of vegetable life, seem to 

 have resembled, in the group, 

 and in at least their more 

 prominent features, the Algce 

 of the existing time. And 

 with the first indications of 

 land we pass direct from the 

 Thcdlogens to the Acrogens, 

 — from the sea-weeds to the 

 fern - allies. The Lycopo- 

 diacece, or club-mosses, bear 

 in the axils of their leaves 

 minute circular cases, which 

 form the receptacles of their 

 spore-like seeds. And when, 

 high in the Upper Silurian 

 system, and just when pre- 

 paring to quit it for the 

 Lower Old Red Sandstone, 

 we detect our earliest ter- 

 restrial organisms, we find that they are composed exclu- 

 sively of those little spor - e-receptacles. 



" The existing plants whence we derive our analogies in 

 dealing with the vegetation of this early period, contribute 

 but little, if at all, to the support of animal life. The 

 ferns and their allies remain untouched by the grazing 

 animals. Our native club-mosses, though once used in 

 medicine, are positively deleterious ; horsetails (Equise- 

 tacece), though harmless, so abound in silex, which wrap 

 them round with a cuticle of stone, that they are rarely 

 cropped by cattle ; while the thickets of fern which cover 

 our hill and dell, and seem so temptingly rich and green 



Fig. 204. 



Woody fibre from the root of the 

 Elder, exhibiting small pores. 2, 

 Woody fibre of fossil wood, showing 

 large pores. 3, Woody fibre of fossii 

 wood, bordered with pores and spiral 

 fibres. 4, Fossil wood taken from coal 



