THE FLORA OF THE COAL FORMATION. 445 



the surfaces of the shales, resembling flowers. Its stems were very- 

 slender, but branching copiously, and bearing wedge-shaped leaves 

 often toothed at the edges, and veined in the manner of fern leaves. 

 The spores were borne on small spikes like those of Asterophyllites. 

 Five species have been recognised in the Acadian Coal-fields. I am 

 not aware that this and the two preceding genera contributed to any- 

 great extent to the accumulation of coal ; but as their tissues were 

 scalariform, similar to those of ferns, it would not be easy to recognise 

 them. A beautiful spechnen of Sphenophjllian emarginatum from 

 New Brunswick, in the collection of Sir W. E. Logan, has enabled 

 me to ascertain that its stem had a simple axis of one bundle of 

 reticulato-scalariform vessels, like those of Trncsipteris as figured by 

 Brongniart. These curious plants were no doubt cryptogamous, 

 having a habit of growth like that of Equisetacece, leaves like those 

 of ferns or Marsiliacece, and fructification and structure like those of 

 Lycopodiacecu (Fig. 165, C). 



6. Pinnularia. — These are slender roots, or stems branching in a pin- 

 nate manner, and somewhat irregularly. They are very abundant in 

 the coal shales, and were probably not independent plants, but aquatic 

 roots belonging to some of the plants last mentioned. The probability 

 of this is farther increased by their resemblance in miniature to the 

 roots of Calamites. They are always flattened, but seem originally 

 to have been round, with a slender thread-like axis of scalariform 

 vessels, enclosed in a soft smooth cellular bark (Fig. 165, D). 



2. Filices or Ferns. 



The ferns or brackens are still very abundant in the forests of 

 Acadia, but do not constitute nearly so prominent a part of the flora 

 as in the days of the Coal formation, when the species were vastly 

 more numerous in proportion to other plants, and when there were 

 tree ferns similar to those of the present tropics and southern hemi- 

 sphere, as well as the smaller herbaceous species. The fronds of fossil 

 ferns are often well preserved, but we usually obtain them only in 

 fi-agmcnts and destitute of the fructification, which is the most distinc- 

 tive character in living ferns. Hence we are obliged to arrange the 

 fossil ferns in an arbitrary manner ; the stems, when found, by tliem- 

 sclves and the fronds by themselves, and tlic latter in groups based 

 on venation and other comparatively unimportant characters, rather 

 than on fructification. The classification thus formed is altogether 

 provisional, and when our knowledge of the subject shall become more 

 complete, must give way to one of a more natural character. In the 



