18 THE UNCOILING FRONDS. 
more mature than the first ones from the prothallium 
and will produce spores much sooner, being born 
“srown up” as one might say. In this plant, the bul- 
blets seem to be the chief means of continuing the 
species,while the spores 
travel about seeking 
new territory. Some 
species send out stolons 
which form new plants 
at their tips; others 
produce tubers upon 
their roots that may be- 
come new plants; and 
still others root at the 
tips of the fronds. 
None of them, however, 
VENATION OF A PINNA IN ASPIDIUM. are lacking in the ordi- 
nary means of propagation. A tropical species of 
Nephrolepis has both tubers and stolons. 
A frond that bears sporangia is called fertzle to dis- 
tinguish it from the unfruitful or sterz/e ones. In a large 
number of species the two are scarcely different, except 
for the presence of sporangia, but in others the fertile 
are more or less changed in appearance and reduced in 
size. 
When the blade of a frond is divided entirely to the 
midrib, it is said to be peunate and the divisions are 
called pinne@. When the pinne themselves are divided 
to the midrib, the frond is said to be dz-piunate and the 
second divisions are called pzunules or secondary pinne. 
When frond or pinna is not completely pinnate, it is said 
to be pennatifid and the divisions are segments. A frond 
may be several times pinnate or pinnatifid in which case 
