THE CLUB-MOSSES 159 



enough to produce their organs of reproduction. 

 In these native species and some others the pro- 

 thalli are subterranean, the spores getting washed 

 deep down into the ground before they germinate. 

 There is no chlorophyll, and a very curious point 

 is that the prothalli cannot develop properly 

 unless they are infected by a Fungus, which 

 penetrates their tissue and lives on terms of 

 mutual benefit with its host a remarkable 

 arrangement, which, however, is not at all un- 

 common in other cases (see Chapter II). 



This does not, however, apply to all Lycopo- 

 diums by any means, for in L. inundatum and 

 various exotic species, the prothallus grows 

 on the surface of the ground, or on the bark of 

 a tree; it has leaf -like outgrowths, and is green 

 in colour and able to look after its own nutrition 

 like other chlorophyll-containing plants. 



In any case the same prothallus produces 

 both kinds of sexual organs. The spermato- 

 zoids differ from those of the Fern-group in 

 having, as a rule, only two cilia each. After 

 fertilisation of an egg-cell by a spermatozoid an 

 embryo develops, which remains for a very long 

 time in connection with the prothallus. 



Phylloglossum, the only other member of the 

 Lycopods with spores of one kind, is a minute 

 Club-moss growing in Australia and New Zea- 

 land; it has a short tuberous stem, a few simple 



