PTERIDOPHYTA 
143 
peculiarity has been recently detected in one of the 
living species of Equisetum. 
Associated with some of the fossil forms there are 
found cones, which evidently 
belong with them, and resemble 
those of the existing Equisetum. 
In a few instances they have 
been preserved so perfectly that 
the inner structure can be accu- 
rately made out, and it is evi- 
dent that the tissues and spo- 
rangia of these plants closely 
resembled those of Equisetum, 
although most of them exhibit 
a degree of specialization not 
found in any of their living 
relatives. The Equisetines rap- 
idly diminish in importance in 
the later geological epochs, until, 
as we have seen, but a single 
genus has survived to the pres- 
ent time, and this is one of the 
less specialized types. 
LYCOPODINEA 
The third class of Pterido- 
part of a plant of a club- 
moss (Lycopoditim clava- 
tum) with two sporangial 
spikes, sp ; B, a sporophyll 
from the spike of L. den- 
droideum, bearing a single 
large sporangium, sp; C, 
cross-section of the stem; 
vb, the central -vascular 
eylinder. 
phytes, the Club-mosses, is intermediate in point of num- 
bers between the two already considered. There are 
three well-marked orders, of which the first, Lycopodi- 
acee, includes the common club-mosses belonging to 
the genus Lycopodium. The second order, Selaginel- 
