1 82 STUDIES IN FOSSIL BOTANY 



only the small spores are known with certainty. They 

 are present in countless multitudes in each sporangium, 

 and are usually found still grouped in fours, with a 

 tetrahedral arrangement. The spores are very minute, 

 about .02 mm. in diameter. From the analogy of 

 other cones of Lepidodendreae there is a strong 

 presumption that L. oldhamius was heterosporous, like 

 Selaginella, the microspores alone having been identified 

 at present. Several forms are known to have been 

 heterosporous, and it is most probable that all Lepido- 

 strobi will prove to be so when we have a more complete 

 knowledge of the strobili. 1 Fragments of a hetero- 

 sporous cone, with large megaspores nearly a millimetre 

 in diameter, have been found in the same beds which 

 have yielded the specimens of L. oldhamius. 



We will, however, choose as our example of hetero- 

 spory in Lepidostrobus a cone from a lower horizon, 

 named Lepidostrobus V eltheimianns , a small species 

 which is very abundant in the plant-bearing beds of 

 the Calciferous Sandstones, near Burntisland, in Scotland. 

 These cones are indistinguishable from those of Lepido- 

 dendron Veltheimianum, one of the few Lepidodendra 

 which have been found with the fructification still 

 attached to the branches. As this species is extremely 

 abundant in the Calciferous Sandstone series, of which 

 the Burntisland beds form part, it is extremely probable 

 that the cones with structure preserved belong to it. 

 Hence I have ventured to use the specific name 

 Veltheimianus for the cones also. For information 



1 In certain cases, the apparently homosporous strobili were doubtless 

 the male fructifications corresponding to the " seed-bearing " cones olLepido- 

 carpon, described below, p. 193. 



