PALEOBOTANY — BERRY. 



315 



(dorsal) sterile lobes. Each of the fertile lobes or sporangiophores 

 bore four radially elongated homosporous sporangia. 



This brief sketch indicates that the Sphenophyllae as we know 

 them represent a diversified and ancient stock clearly related to, but 

 more primitive than the Calamariae. Their relation to the Lepido- 

 phyta was more remote, the latter showing but slight evidence of a 

 megaphyllous ancestry or of sporangiophores, the sporangia being 

 borne directly upon the sporophylls or in their axils. There is con- 

 siderable homology in the stelar anatomy of the two groups and it 

 seems probable, especially with the variations of strobilar morphol- 

 ogy among the Sphenophyllae in mind, that morphologists have 

 magnified the importance of these features as contrasted with those 

 in the Lepidophyta. At any rate, the view is advocated here that 

 both the Arthrophyta and 

 Lepidophyta go back to a very 

 ancient common ancestral 

 s t o c k from which also the 

 Sphenophyllales as we know 

 them were descended. 



The second class of arthro- 

 phytes — the Calamariae, in- 

 clude three orders — namely, 

 the ancient Pseudoborniales, 

 the Calamariales, comprising 

 the large and diversified cala- 

 mites of the Paleozoic, and the 

 Equisetales, sparingly repre- 

 sented in the Paleozoic, some- 

 what more abundant in the 

 Mesozoic, and represented in 

 the existing floras as the sole 

 survivors of the whole arthro- 



phyte phylum. The Pseudoborniales are imperfectly known, being 

 based upon impression from the Upper Devonian of Bear Island de- 

 scribed in the first instance by Heer as Catamites radiatus. The 

 main stems were of considerable size, reaching 10 centimeters in 

 diameter, with nonalternating ribs. The leaves, of relatively large 

 size, were in whorls (probably in fours), short-stalked, and palmately 

 and repeatedly dichotomous. The fructifications were long lax cones 

 with whorled sporophylls resembling reduced vegetative leaves, and 

 the sporophylls bore sporangia on their lower surfaces. These im- 

 portant plants, unfortunately too little known, show decisive evidence 

 of a megaphyllous ancestry. Scott has suggested a comparison with 

 Cheirostrobus based upon the complexity of the latter and the com- 

 pound leaves of Pseudobornia. Irrespective of this somewhat remote 



Fig. 7. — Leaf of Tseudobomia ursina Nathorst from 

 the Devonian of Bear Island. 



