2 3 8 
PHARMACEUTICAL BOTANY 
others on a special stem of slightly different form. In the latter the 
spores are provided with elaters, which, being hygroscopic, coil and 
uncoil with increase or decrease in the amount of moisture present, 
thus aiding in the ejection of spores from the sporangia. The num- 
ber of species is small and included under one genus, Equisetum. 
Fig. i 13. — Selaginella Martensii. a, vegetative branch; 6, portion of the 
stem, bearing cones ( x ) ; c, longitudinal section of a cone, showing microsporangia 
(mic. sp.) in the axils of microsporophylls, and megasporangia in the axils of meg- 
asporophylls; d, microsporangium with microsporophyll; e, microspores; /, por- 
tion of wall of sporangium, greatly magnified; g, megaspore; h, microsporangium 
opened, and most of the microspores scattered; i, megasporangium, with mega- 
sporophyll; k, same, opened, showing the four megaspores. (Gager.') 
SUBDIVISION III.— FILICINE.E 
The group Filicineae is the largest among the vascular cryptogams 
and includes all the plants commonly known as Ferns. The main 
axis of a tvpical fern is a creeping underground stem or rhizome 
