V] 



LEPTOPHLOEUM AND FRUCTIFICATIONS 



67 



Distribution. Middle Devonian to Lower Carboniferous. 



In the specimens from the Middle 

 Devonian of the United States, some of 

 the decorticated stems are markedly ribbed, 

 just as we have seen is the case in Devonian 

 Bothrodendrons. 



Leptophloeum, Dawson, 1862^ (Fig- 40). 

 Stems subarborescent, dichotomously 

 branched, with a spirally arranged armour 

 of leaf bases ; leaf bases of relatively large 

 size as compared with the diameter of the 

 stem, nearly contiguous, rhomboidal, ar- 

 ranged in periods of large rhomboidal 

 bases alternating with periods of much 

 smaller, more transversely elongated bases. 

 Leaf scar very small, situated a little above 

 the middle of the base, oval or ovate, with 

 a single print situated a little above the 

 middle of the scar. Ligular ? pit at apex 

 of base. 



We agree with White ^ in referring the 

 so-called Lepidodendron australe, McCoy, 

 and L. nothum, Unger, of Australia, to this 

 genus. 



Distribution. Devonian, only in Canada, 

 United States, Spitzbergen and Australia. 



Fig. 40. Leptophloeum 

 rhombicuni,Y)a,ws., from 

 the Upper Devonian of 

 the United States. Type 

 specimen (nat. size). 

 After White (1905). 



Isolated Fructifications of Upper Devonian Age. 



The most common types of isolated fructifications occiu-ring 

 in Upper Devonian rocks are those which are clearly similar to, 

 or even generically identical with, the fructifications of species of 

 Archaeopteris. The few other types found, including Xenotheca^ 

 in England and Dimeripteris'^ of Russia and the United 



1 White (1905). 



-Ibid. (1905), pp. 72-3. 



3 Arber and Goode (1915), p. 96, PI. IV, figs. 1-7, 10, 11, Text-fig. 2. 



< White (1905), p. 53. 



