20 
THE FERN WORLD 
its form is described as being pinnatijid, the expression 
being derived from two Latin words — pinna , ‘ a feather,’ 
and findo, ‘ I cleave.’ Should the iucisions reach quite 
down to the racliis, so as to entirely separate the leafy 
divisions, the frond is called pinnate, and each division is a 
pinna , becoming pinnae, in the plural. If, in the same way, 
the pinnae are again divided, the term bi-pinnate is applied 
to the frond. When this mode of division is continued 
through another stage, the frond is termed tn-pinnate. If 
the frond be more than thrice divided, it is described as 
being de-compound. A pinnule is the next subdivision of a 
pinna, and a lobe the division of a pinnule. 
It is the fronds of Ferns which afford the most ready 
means of distinguishing them from other plants, and the 
signs of distinction are principally two. The first which 
may be noticed is the curious way in which fronds are, 
not folded, but rolled in. When they first start from the 
crown, they have somewhat the appearance, as they push 
above' it, of a nest of little scaly balls. As they grow 
upwards, they look like scrolls in process of unrolling, or 
like the uncoiling of a watch-spring. If the frond be simple 
and undivided, the unrolling upwards goes on until the 
whole stipes and leafy portion have been rolled outwards 
from the base of the stipes to the apex of the frond. If it 
be a pinnate, bipinnate, or tripinnate frond, the pinnae, 
pinnules, and lobes are similarly rolled out from their bases 
to their apices. It is curious to note in the compound fronds 
that the processes of unrolling in their upper parts and in 
their lower or basal pin me take place almost simultaneously ; 
for so soon as the first upward unrolling in the direction 
indicated by the stipes and the principal racliis has liberated 
the lowest pinnae, these commence to unroll, whilst the 
primary unrolling is continuing upwards : and the next and 
succeeding pinna) above the lowest commence one after the 
