162 PLANT-LIFE 



of spermatozoids possessing two cilia, which are thus 

 different from the multiciUate male elements of the 

 Ferns. Existing species are arranged into four families 

 — the Lycopodiacece, Psilotacece, SelaginellacecB, and 

 IsoetacecB ; two other families, the Lepidodendracece and 

 SigillariacecB, occur only in fossil forms. 



Lycopodiacece. — This family includes those species 

 which have gained popular recognition, and have 

 secured the appellation, " Club-Mosses." Between 90 

 and 100 species have been distinguished, and five of 

 them are found in Britain. The Common Club-Moss, 

 Lycopodium clavatum, sometimes called " Stag's-Horn " 

 Moss, is generally distributed over Britain on heaths and 

 hill-pastures; its range extends from the Pyrenees and 

 the Alps to the Arctic regions, and it is found in North 

 America. The hard creeping stems, with forked branch- 

 ings, are covered with small awl-shaped leaves; forked 

 roots are sent into the ground from the under side of 

 the stem, while from above leafy branches ascend into 

 the air. Conelike aggregations of sporophylls (spore- 

 leaves) occur at the tips of the erect shoots. The sporo- 

 phylls are somewhat broader than the ordinary leaves ; 

 they bear kidney-shaped sporangia, one at the base of 

 each, on the upper side. The sporangia are relatively 

 large, very much larger than those produced by Ferns. 

 The Fir Club-Moss, Lycopodium selago, also occurs in 

 hill-pastures in Britain; it ranges in the cold and tem- 

 perate countries of both hemispheres. This species is 

 peculiar in that its forked stems are always erect, and 

 there is no distinction between the spore-bearing and 

 sterile parts of the shoots. L. alpmum is rare in Southern 

 England ; but it is found in mountain pastures from the 



