ACROGENS. 279 
In order to study more closely the structure of a fern, let us 
examine the Nephrodium filix-mas., commonly known as the male 
fern (Fig. 339). 
This plant is common in the woods and sterile places. It carries 
upon its subterranean stem, which creeps along horizontally, cer- 
tain reddish scales. The leaves are large, petiolate, and much 
intersected. On the under surface of the leaves, or of what has the 
appearance of leaves, and which, as already stated, are called in 
the language of botany, fronds, we find little rounded, or, rather, 
kidney-shaped projections. Each of these projections are formed 
by groups of small bodies, yellowish green at an early age, brown 
ig. —— of the Fig. pias ona of 
at their maturity, and which are covered by a thin greyish 
pellicle. Each group of these little bodies or sporanges bears 
the name of sori; the pellicle which covers them is called the 
indusium. Fig. 341 is a greatly magnified representation of the 
— which occur on the lower surface of the fronds of the male 
ern. : 
The sporanges or capsules (Fig. 842) are pedicellate cellulose 
sacs, furnished on their circumference with an almost entire circle 
of cellules, larger and thicker than the other parts of the wall. 
These cellules form a sort of ring, which by growth, or by certain 
hygrometric changes, seem to determine the irregular rupture 
of the walls of the capsule (Fig. 343), and by these movements: 
Pour out a number of egg-like irregular globules, which were 
considered to be the seeds of the plant, and were called 
‘pores. But this assimilation is ascertained to be absolutely 2 
