314 



LYCOPODIUM 



genera Lycopodinni (Fig. 179) and Selaginella (Fig. 180). Tlie 

 Quilhvort (Isoetes lacitsiris, Fig. 178), which occurs submerged 

 in mountain tarns, is a pecuhar member of this group, many of 

 whose features recall those of the fossil Clubmosses (Lcpido- 

 dendron and Sigillaria, Fig. 177). Fragments of the stems of 



the ffH'mer with, or often 

 without, the leaves, are 

 very conunon in the Coal 

 Measures and are readily 

 identified bj- their charac- 

 teristic markings (Fig. 



17.5. g. 



The small spirally ar- 

 ranged leaves of Lyco- 

 podiinn densely clothe the 

 stems, \\-hich are either 

 erect, as in the Fir Club- 

 moss [L. sdago), or pros- 

 trate, except for the 

 cone-bearing shoots, as in 

 the Bear's Foot [L. clavatum , 

 Fig. 179, A) The stems, 

 as well as the occasional 

 adventitious roots, exhibit 

 forked branching, and 

 never contain more than a 

 single stele, 1 whose detailed 

 structure is often some- 

 what complex. The sessile 

 leaves are attached bj' a 

 broad cushion-like base, 

 and are traversed by but 

 a single median vein (big. 179, B) ; the same was the case in 

 Lcpidodcndron, the persistent leaf-cushions affording the dis- 

 tinctive markings above referred to. The British species of 

 Lvcopodium are found in nmist ujiland pasture, except for 

 /,. imittdcdiim, which occiu's in lowland bogs. 



1 A .single stele was likewise found in LcpidoJeiidro}! where, however, it 

 became enveloped by a broad zone of seeondary wood and phloem. 





Fig. 177. — Kestoration of various fossil 

 Clubnrosses (Lepidodeiidroii and 

 Sigillaria). (.'\fter Grand Kury.) 



