THE FERN ALLIES. 



35 



shaped. As the plant retains t-his power indefinitely, it has 

 sometimes been called " the Resurrection-plant." 



93. The stems are usually creeping, yet in some species 

 show a tendency to become erect, and most species send up 

 erect branches which bear the fruit. Most species bear roots 

 at irregular intervals along the under side of the creeping stems, 

 but our solitary species of Psilotum is rootless, bearing only 

 underground shoots which perform the functions of roots. The 

 leaves are small and unbranched, in some instances resembling 

 appressed scales, in others resembling the acicular leaves of 

 Conifers, and are arranged in four, eight, or many ranks. In 

 some species the leaves are of one kind, while in others two or 

 even more forms may occur on the same plant. In Psilotum 

 the leaves are all rudimentary. 



94. Fructification. The fructification of the club-mosses 

 is chiefly borne on upright branches in solitary or clustered 

 (2-5) spikes, which are formed of numerous scales or scale- like 

 leaves, each bearing a single large sporangium in its axil. The 

 sporangia open transversely, and are 



one-celled, except in Psilotum, where 

 they are three-celled. In a few species 

 of Lycopodium the sporangia are borne 

 near the summit of the fertile stems 

 in the axils of ordinary leaves. The 

 usual shape of the fruit-bearing scales 

 is represented in Figs. 24-26. 



95. The spores of Lycopodium 

 and Psilotum are of one kind (Fig. 24), 

 but in Selaginella two kinds of spo- 

 rangia are developed the microspo- 

 rangia, producing numerous micro- 

 spores (Fig. 25) not unlike the spores 

 of Lycopodium; and the macrospo- 

 rangia, producing usually four macro- 



Spores (Fig. 26), SO called from their b eannga sporangiumin itsaxil. 



. FIGS. 25, 26. Scales from fer- 



larger Size. ThlS Character of Sela- tile spike of Selaginrlla rupes- 



ginella, which it shares with the quill- i^**j*$^^ 

 worts and pepperworts soon to be described, serves as the 

 basis for the division of the fern allies into two groups : the 



