NOTES ON THE LEPIDOCARPACEAE 551 



world. This may be explained, in part at least, by the fact that the best fossil- 

 iferous (coal ball) deposits in America are younger than those most studied 

 in Europe, and these younger beds may contain representatives of the family 

 at the apex of its geologic history. 



The Genus Lepidocarpon 



Lepidocarpon Scott, first recognized and denned about forty years ago, is 

 the type genus of the Lepidocarpaceae. Scott's original diagnosis (Scott 1900, 

 p. 309) is as follows: 



Lepidocarpon, gen. nov. — 



Strobilus, with the character of Lepidostrobus, but microsporangia and megasporangia 

 each surrounded by an integument, growing up from the upper surface of the sporophyll. 

 Megasporangium completely enclosed in the integument, except for a slit-like micropyle 

 along the top. A single functional megaspore developed in each megasporangium. Sporo- 

 phyll, together with the integumented megasporangium, detached entire from the strobilus, 

 the whole forming a closed, seed-like, reproductive body. 



It is proposed to name the coal measures form Lepidocarpon Lomaxi and that from 

 Burntisland L. IVildianum. Both were included by Williamson under his Cardiocarpon 

 anomalum, which however, is quite different from the seed so named by Carruthers. 



Scott also noted on page 307 that "the outer layer of the sporangial wall 

 has the columnar or palisade-like structure characteristic of Lepidostrobus; it is 

 lined by a more delicate inner layer which may be several cells thick." 



In the diagnosis published with his more complete treatment of Lepidocar- 

 pon (1901), Scott omitted mention of the microsporangiate structures because 

 he was more doubtful of their relationship than he had been previously. The 

 main points of his later diagnosis are as follows: 



(1) Strobilar habit — like Lepidostrobus; 



(2) Integuments present when mature; 



(3) Megasporangium entirely enclosed except for micropylar slit; 



(4) A single functional seed megaspore nearly fills the sporangial cavity; 



(5) Sporophyll became detached from the cone axis as a unit. 



To these an additional point may be added from p. 304 of Scott's detailed 

 description. 



The structure of the sporangium is however the same, as in its naked condition 

 [e.g., in Lepidostrobus] . The wall has a superficial columnar layer, with a more delicate 

 lining tissue within it. The cells of the columnar layer are often shorter and broader 

 than in the non-integumented sporangium [of Lepidoacrpon lomaxi] owing no doubt to 

 superficial extension of the wall ; at other places, however, and especially at the apex 

 where the narrow ridge of the sporangium fits into the micropylar opening, the structure 

 is quite unchanged. 



In defining Lepidocarpon the writer considers it advisable to follow Scott's 

 generic interpretation rather carefully. The diagnosis provided by Scott in 1900 

 and slightly emended in 1901 may well be altered, however, so that it will 

 reflect some of the additional observations made by various workers during the 

 last forty years of sporadic study of this group of plants. It is now possible to 

 refer compression and impression specimens to this genus and with the progres- 

 sive elimination of non-biologic differences (resulting from differences of pres- 



