DISTRIBUTION OF PLANTS. 113 



to-day found growing only in warm latitudes. A Tree-fern 

 of the Coal-measures, called Megaphyton, had its large fronds 

 in two vertical ranks ; other common genera were Cyclopteris, 

 Odontopteris, Neuropteris, etc., whose leaflets, or pinnae, were 

 destitute of a midrib; Sphenopteris, Hymenophyllites, etc., 

 whose pinnae had a midrib discernible only toward the base, 

 and from which the veins did not branch ; Alethopteris, Pe- 

 copteris, Asplenites, etc., whose pinnae presented a distinct 

 midrib, from which the nerves branched more or less ob- 

 liquely (Fig. 132). 



(c) Lycopodiacese. — The Lycopods were represented by huge 

 Lepidodendra (Fig. 131) and other nearly-related genera, as 

 well as by the gigantic Sigillarise. The roots of these plants 

 are often found fossil, and are distinguished by scattered, 

 rounded depressions or elevations. These were formerly be- 

 lieved to be the leaf-scars on stems and branches ; and the 

 genus Stigmaria was formed to include them. They are yet 

 designated by this name, but they have in many cases been 

 found attached as roots to the Lepidodendra and Sigillariae. 

 Fruits have also been found, generally isolated, but they are 

 believed to be the fruits of the preceding plants. 



(d) Coniferas. — Fossil Conifers are found in the form of 

 stumps, logs, leaves and fruits. They were very unlike the 

 present Conifers of the temperate climates. They resembled 

 more or less the tropical Araucaria, the broad-leaved Chinese 

 Salisburia (Maiden-hair tree), or the curious two-leaved Afri- 

 can Welwitschia. A very interesting genus is that of Cor- 

 daites. It had a straight trunk, sometimes sixty to seventy 

 feet long, and was clothed with long strap-shaped leaves. 



5. In the early part of the ReptUian Age (during the Tri- 

 assic and Jurassic eras), the flora differed from the preced- 

 ing age mainly in the enormous development of the Gym- 

 nosperms. These, the Cycads (appearing for the first time) 

 and Conifers, together with the Tree-ferns, constituted the 

 forest vegetation. There were also new species of Ferns and 

 Equiseta. Diatoms and Desmids were abundant. But it is 

 in the latter part of this age (during the Cretaceous era) 



