19 1 9] BASSLER—SPQRANGIOPHORIC LEPIDOPHYTE 87 



In 1872 Williamson (37) described and figured a Lepidostrobus 

 {L. Veltheimianus Scott) in which a single continuous plate of 

 sterile tissue usually in a median position arises from the slightly 

 projecting subarchesporial pad and extends upward into the sporan- 

 gial cavity. Williamson believed it to be "coextensive with the 

 entire length of the sporangium," but Bower (5) figures a section 

 in which it does not extend quite to the distal extremity. In 19 14 

 Mrs. Agnes Arber (i) demonstrated the presence in Lepidostrobus 

 Oldhamius Willm. of a similar plate of sterile tissue which also 

 "died out toward the distal end of the spore sac," and the same 

 structure was observed by this author in L. foliaceous Maslen, 

 L. Binneanns Arber, and in an unnamed species from the Coal 

 Measures of Great Britain discussed and figured by Bower in 

 1894. Bower also called attention to the irregular trabecular 

 processes that "spring upwards from the floor of the sporangium 

 (of Lepidostrobus Brownii) and project a considerable distance into 

 the cavity. They are not scattered indiscriminately over the floor 

 of the sporangium, but arise from a projecting ridge." Renault 

 (21) shows similar structures in the sporangium of L. Rouvillei 

 Sap. and Ren. from the south of France. Accordingly Mrs. Arber 

 concludes that "some form of sterile upgrowth from the sporangial 

 floor may eventually prove to be characteristic of all forms of 

 Lepidostrobus which are homosporous or microsporous, such a 

 structure not yet having been observed in megasporangia." 



The median sterile plate in the sporangium of a number of 

 species of Lepidostrobus is singularly suggestive of that median 

 plate in Canthelioplwrus which constitutes the sporangiophore, 

 but even should we accept their homology, and this we may not so 

 easily escape, this fact, if considered without reference to other 

 facts, could as well be adduced in support of one as of the other of 

 the opposing phyletic theories of reduction and amplification. 

 Are there any facts which might suggest to us the course of the 

 events in the descent of these groups ? Facts from ontogeny are 

 of the utmost importance in the solution of phyletic problems, but 

 from the very nature of fossils such facts are not usually available. 

 We are fortunate, however, in having a few facts concerning the 



