344 SIGNIFICANCE OF PHYLLOGLOSSUM 



fir or hemlock (Fig. 236). These plants are very well repre- 

 sented in our open woods, where they often form conspicuous 

 colonies owing to the extensive branching and prolonged growth 

 of the stems which creep over or through the ground, sending 

 up numerous, erect branches and giving off roots that branch 

 with great regularity. Various species of Lycopodium are ex- 

 tensively gathered for decorations since the aerial portions of 

 the stems are thickly clothed with small moss-like leaves. The 

 second genus of the family (PhyUoglossum) contains but one 

 species, which is found in New. Zealand and Australia. It is of 

 interest because it is the most simple fern known (Fig. 238), 

 consisting of a few narrow leaves, rudimentary strobilus and 

 poorly developed tissues. The simple strobilus of this plant is 

 suggestive of the sporophyte of Anthoceros and it also recalls the 

 spore-bearing spike of Ophioglossum. If the sterile cells separat- 

 ing the spore-forming cells in Anthoceros had increased in number 

 so as to project somewhat and thus form rudimentary leaf -like 

 outgrowths, then it Avould have resembled the strobilus of PhyU 

 loglossum. To be sure the sporangia of the latter plant are borne 

 upon the leaves but in the next family they arise from the stem 

 as in Anthoceros. Ophioglossum shows the increase of the sterile 

 cells between the spore-bearing cells but this did not result in 

 leaf development; so it occupies an intermediate position in this 

 trend of development. It is certainly a striking fact that these 

 three groups, though widely separated, exhibit the same type of 

 development. 



The sporangia of the Lycopodiaceae are large considering the 

 size of the leaf, and usually appear on specialized leaves that are 

 arranged in strobili on the ends of erect branches (Fig. 239). 

 The sporangia open by a longitudinal cleft and the spores are 

 produced in such quantities in some of the forms that they are 

 of commercial importance, being used for flashlight effects and 

 sold as lycopodium powder. 



(a) The Gametophyte of the Lycopodiaceae. — The most inter- 

 esting feature about the club mosses is the sexual generation, 

 because it indicates that these forms may have been derived from 

 the same ancestry as the mosses or at least from a very primitive 



