162 PLANT-LIFE 



of spermatozoids possessing two cilia, which are thus 

 different from the multiciliate male elements of the 

 Ferns. Existing species are arranged into four families 

 the Lycopodiacece, Psilotacece, Selaginellacece, and 

 Isoetacece ; two other families, the Lepidodendracece and 

 Sigillariacece, 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. alpinum is rare in Southern 

 England ; but it is found in mountain pastures from the 



