THE CLUB-MOSSES 177 



Trunks of the other principal genus, Sigil- 

 laria, have been found of almost equal height 

 and similar proportions; in some, however, the 

 form was shorter and sturdier; a German Sigil- 

 laria is described, which was 6 feet in diameter at 

 the base and only 18 feet high, diminishing to a 

 thickness of about a foot at the top. 



In habit the tree Club-mosses most resembled 

 Lycopodium, but in their mode of reproduction 

 they agreed rather with the Selaginellacese. No 

 doubt their true affinities were closer with the 

 latter group, though there was no near relation- 

 ship to Selaginella; as we have seen, the latter 

 type was, for all we know, as ancient as the 

 Lepidodendreae themselves, and there is nothing 

 directly connecting the two groups. 



The Lepidodendrese (using the name to include 

 Sigillaria as well as other less important genera) 

 were already well developed in Devonian times, 

 and extend right through the Carboniferous and 

 Permian, becoming rare and doubtful when we 

 reach the Mesozoic rocks. 



In habit the two principal genera, Lepido- 

 dendron and Sigillaria, were different. Both had 

 an upright, usually lofty stem, but Lepidoden- 

 dron was freely branched, and consequently had 

 to some extent the aspect of our familiar forest 

 trees (see fig. 20), while Sigillaria branched very 

 sparingly, or in some species not at all, and thus 



