PALEOBOTANY — BEERY. 379 



North America, Europe, the Arctic, and possibly present in China, 

 is Archaeopteris. It includes a considerable number of species and 

 appears to have survived into the LoAver Carboniferous of Spain 

 and elsewhere. 



Archaeopteris shows considerable variation in the details .of its 

 organization. Its fronds were large, occasionally a meter in length, 

 bipinnate with stipules at the base of the stipe. Sterile pinnules 

 cuneate or obovate with entire or variously toothed or laciniate mar- 

 gins and dichotomously fiabellate veins. The fertile pinnules borne 

 on the same fronds with the sterile pinnules had their laminae 

 greatly reduced and carried sessile or short-stalked large oval 

 sporangia in groups of twos or threes. The latter are usually re- 

 garded as exannulate, and consequently Archaeopteris was formerly 

 considered to ha've been a marattiaceous fern, although latterly, 

 many students regard it as probably a pteridosperm. (PL 4.) • 



The Pteridosperms were also probably represented in the Devo- 

 nian by the structural materials known as Kalymma petioles, and 

 by the genera Cladox}don and Calamopitys representing two dif- 

 ferent family types. The Lepidophyte phylum included Devonian 

 species of Lepidodendron, Leptophloeum and Lepidostrobus and an 

 abundance and variety of Bothrodendraceae referred to the genera 

 Porodendron and the cosmopolitan Bothrodendron. An idea of their 

 abundance may be surmised from the fact that the so-called paper 

 coal of central Russia is made up largely of their stem cuticles. 

 One of the most exceptional Devonian plants and the largest known 

 pre-Carboniferous tree is Protolejndodendron primaevum, which 

 was found in the Portage beds near Naples, New York (fig. 28). 

 The expanded butt shows that some secondary wood was probably 

 formed. The roots are gone but Stigmaria-like rootlets, were pre- 

 served. At the base of the trunk the leaf scars are irregular. Above 

 the base they are closely spaced on pronounced vertical ribs as in 

 the Favularia type of Sigillarias. Higher up the ribs die out, the 

 scars become rhomboidal, and bolsters appear until typically spirally 

 arranged lepidodendron scars have replaced the Sigillaria type. 



The leaves were persistent, about 3 cm. long, dilated at the base 

 as in Bothrodendron, and lax or recurved. The leaf scars are on the 

 most prominent part of the bolsters, oval in form, and show an upper 

 or ligular scar, a central leaf trace scar, and on either side of the 

 latter large lunate parachnoi. This remarkable type belongs to tlra 

 group that includes similar forms often referred to the genus 

 Archaeosigillaria, and represented in the Devonian of New York, 

 Pennsylvania, Norway, England, Bohemia, and German} 7 . Phylo- 

 genetically they appear to lie halfway between Bothrodendron and the 

 Rhytidolepis Sigillarias. The genus Psilophyton which characterizes 

 the Devonian of North America and Europe is very imperfectly known 



