THE PENNSYLVANIAN PERIOD 



383 



FIG. 403. Leaflet of 

 a seed fern from the 

 Coal Measures of 

 Pennsylvania. 



tamarack and rushes, were in existence then. The prevalent 

 plants were the seed ferns (Fig. 403) with some true ferns and 

 other pteridophytes (see p. 293). They 

 were free to occupy all the stations in 

 life now held by the higher seed plants. 

 Some were low herbs, like our modern 

 ferns, while many had developed woody 

 trunks with bark, and these rivaled our 

 present day trees in stature. The nu- 

 merous stumps and fallen logs which 

 have been found embedded in the coal 

 show that extensive forests of these trees 

 (Fig. 404) were common in both the 

 United States and Europe, as well as in 

 the tropics. The graceful fronds which 

 crowned the palmlike trees may often 

 be found matted between layers of shale, 

 where they have been preserved as in a 

 botanist's press. We can gain a fair idea of the aspect of 

 the Carboniferous forests by comparing the tree ferns which 

 still inhabit New Zealand and Australia. 



With the seed ferns were mingled dense thickets of reeds, 

 resembling our familiar horsetail grass (Equisetum). Many 

 reached the size and perhaps the strength of the tall bamboo 

 of Asia, although their modern descendants are of lowly 

 stature. 



Probably the largest trees of the period were the so-called 

 " scale trees " (Lepidodendron and others). Unlike the pre- 

 ceding forms, the trunks branched as in our familiar elms, 

 and instead of broad, feathery fronds their leaves were short 

 and stiff, and were attached closely to the trunk and branches. 

 The nearest living relative of the Lepidodendron is the trailing 

 club moss (which is not a true moss at all), one of the frailest 

 little herbs of our modern forests. 



Higher plants appear. Thus far all the coal plants which 

 have been mentioned have been members of the Pteridophyte 



