THE CLUB MOSSES 329 



are situated the sexual organs. The prothallia are normally dioe- 

 cious, that is, male and female in sex, but since the spores are 

 distributed in groups, antheridial plants are likely to develop in 

 the same cluster with the archegonial. The sexual organs are 

 sunken in the tissues of the gametophytes. The sperms are 

 coiled, many-ciliate protoplasts (Fig. 285, B) resembling those 

 of the common ferns. 



The early stages in the development of the young Equisetum 

 sporophyte from the fertilized egg are the same as those of the 

 common ferns. This together with the similar gametophytes 

 and sperms is believed to indicate a distant relationship between 

 the Equisetinece and Filicinece, even though the mature sporo- 

 phytes of the two groups appear so different in structure. 



CLASS III. THE CLUB MOSSES, OB LYCOPODINE^E 



319. The club mosses. The Lycopodinece take their common 

 name of club mosses from the moss-like appearance of the stems, 

 which in most forms are covered with small leaves (Figs. 286, 

 289, A), and the fructification, which is generally a club-shaped 

 cone developed at the end of the stem (Figs. 287, A\ 289, A). 

 Isoetes (Fig. 291) is, however, in these particulars a conspicuous 

 exception. But the club mosses are very much larger than any 

 of the true mosses (Musci), and are of course sporophytes, like 

 the horsetails and ferns, while the true mosses are gameto- 

 phytes. Like the horsetails, they are the remnants of a very 

 ancient group which formed forests in the Carboniferous Age 

 (Plate VIII, 3, 4) ; also, they have been able to persist only by 

 adapting themselves to life conditions where they do not en- 

 counter keen competition with grasses and herbs. Almost all 

 of the Lycopodinece are contained in three genera : Lycopodium 

 (about 100 species), Selaginella (about 500 species), and Isoetes 

 (some 60 species). But in addition there are several remark- 

 able types (Pliylloglossum, Psilotum, Tmesipteris) which are 

 tropical or sub-tropical and cannot be described here. 



