FOSSIL PLiNTS OF THE CAEBONIFEEOUS SYSTEM. 



731 



meet with rhizomes. Characters taken from the venation and forms 

 of the fronds are not always to be depended upon, if we are to judge 

 from the Ferns of the present day. There is a great similarity 

 between the carboniferous Ferns of Britain and America. In the 

 English Coal-measures the species are 140. The preponderance of 

 Ferns over flowering plants is seen at the present day in many 

 tropical islands, such as St. Helena and the Society group, as well as 

 in extra-tropical islands, as New Zealand. In the latter. Hooker 

 picked.'jSe kinds in an area of a few acres; they gave a luxuriant 

 aspect to the vegetation, which presented scarcely twelve flowering 

 plants and trees besides. An equal area in the neighbourhood of 

 Sidney (in about the same latitude) would have yielded upwards of 

 100 flowering plants, and only two or three Ferns. This Acrogenous 

 flora, then, seems to favour the idea of a humid as well as mild and 

 equable climate at the period of the coal formation — the vegetation 

 being that of islands in the midst of a vast ocean. 



Among the Ferns found in the clays, ironstones, and sandstones 

 of the Carboniferous period, we shall give the characters of some by 

 way of illustration. Sphenopteris {dipriv, a wedge, and 'xri^ig, a fern) 

 has a bi-tripinnatifid frond, pinnae narrowed at the base (cuneate), not 

 adherent to the rachis, lobed, veins generally arranged as if they radi- 



Fig. 909. 



Kg. 910. 



ated from the base (fig. 908). In Pecopteris {irixw, I comb), the 

 frond is pinnatifid or bi-tripinnatifid (often pectinate), pinnse adnate 



Fig. 908. Sphenopteris HGenninghausii, a'fern of the Carboniferous system. Fig. 909. 

 Pecopteris aquilina, another fern. Fig. 910. Neuropteris Loshii, another fern. 



