
PTERIDOPHYTA 
399 
sealelike and borne in whorls (Figs. 440, 441). The sporangia are 
found on specialized leaves (sporophylls) which occur in terminal 
strobili, — conelike aggregations of sporophylls (Figs. 440, 441). 
This class of plants is unimportant in our present flora, but in past 
geologic ages it was represented by numerous large trees. These 
were important constituents of the forests of the Carboniferous 
period. 
CLASS LYCOPODINEAE (CLUB MOSSES) 
The most important orders of the Lycopodineae are the Lyco- 
podiales and the Selaginellales. The class Lycopodineae is an 
unimportant constitu- 
ent of our present flora, 
but, like the Hgquiseti- 
neae, was represented in 
the Carboniferous Age 
by large trees which 
were prominent con- 
stituents of the forests. 
ORDER LYCOPODIALES 
Lycopodium. ‘The 
genus Lycopodium is 
by far the commonest 
and most widespread 
in this order. In all 
the species the sporo- 
phyte is a small plant, 

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Fic. 447. Portion of a plant of Selaginella with 
sporophylls aggregated in terminal strobili. (x1) 
the stems of which are more or less thickly covered with small, 
pointed leaves (Figs. 442, 443). The sporangia are borne singly 
on the upper surface near the base of a leaf (Fig. 444). The 
sporophylls (leaves with sporangia) may resemble the ordinary 
leaves and be scattered over the stem (Fig. 442), or they may 
be somewhat different in shape and be aggregated in terminal 
strobili (Fig. 443). The gametophyte is a small thallus. 
