REPRODUCTIVE ORGANS OF FILICES. 365 
arrangementas perhaps, upon the whole, the simplest, and from 
its being the one most commonly in use, at least in practical 
Botany. 
1 Friices or Ferns.—The fructification of these plants con- 
sists of little somewhat rounded cases, called sporangia, capsuies, 
or thecx (fig. 802, sp), containing spores in their interior, and 
springing commonly from the veins on the under surface or 
back of their leaves or fronds (figs. 802 and 803); or, in some 
few instances, as in Acrostichwm, from their upper surface ; and 
in others, as in Hymenophyllum, from. the margins. The 
sporangia are arranged in little heaps called sori, which vary 
much in form (figs. 802, sp, and 803, s); these are either naked, 
as in Polypodium (fig. 802), or covered by a thin membranous 
layer continuous with the epidermis, which is called the indusiwm 
Fic. 802. Fic. 803. Fic. 804. 
Fig. 802. A portion of a frond of the common Polypody (Polypodium vul- 
gare), showing two sori springing from its veins. The sori are naked, 
and consist of a number of sporangia or capsules, sp, in which the spores 
are contained. 7g. 803. Portion of a frond of the Male-fern (A spidium 
Filix-mas), with two sori, s, s, covered by an indusium. Fig. 804. 
Portion of a frond of the Royal or Flowering-fern (Osmunda regalis), 
with its sporangia or capsules arranged in aspiked manner on a branched 
rachis. 
or inwolucre, asin Aspidiwm Filix-mas (fig. 803). Sometimes the 
sporangia are so densely compacted that no intervening paren- 
chyma can be distinguished—the latter being destroyed by the 
excessive development of the former ; in which case, instead of 
being collected in sori on the back of the fronds, they appear as 
little bodies arranged in a spiked manner on a simple or 
branched rachis, as in Osmunda (fig. 804). 
The sporangiwm or capsule is a little cellular bag or case (fig. 
805, s), usually stalked, p, and more or less completely sur- 
rounded by a ring or annulus; this ring is frequently elastic, 
and thus causes the bursting of the sporangium when ripe, and the 
escape of its contained spores. In some Ferns the ring is im- 
periect, and in-others it is altogether wanting ; hence Ferns 
