CHAP. III. 
FERNS. 
\ 
221 
ginate, either upon the cuticle or from beneath it, in the form 
of spots, at the junctions, margins, or extremities of the veins. 
As they increase in growth they assume the appearance of 
small heaps of granules, called sori ; if examined beneath the 
microscope these granules, commonly called capsules^ thecce^ spo- 
rangia^ or conceptacles, are found to be little brittle compressed 
bags formed of cellular membrane, partially surrounded by a 
thickened longitudinal ring {gyrus, annulus, gyroma), which at 
the vertex loses itself in the cellularity of the membrane, and 
at the base tapers into a little stalk : the thecae burst with 
elasticity by aid of their ring, and emit minute particles named 
sporules, from which new plants are produced ; as from 
seeds, in vegetables of a higher order. Interspersed with these 
thecae are often intermixed articulated hairs; and, in those 
genera in which the thecae originate beneath the cuticle, the 
sori, when mature, continue covered with the superincumbent 
portion of the cuticle, which is then called the indusium or 
involucrum (membranula, Necker ; glandulcB squamosce, Guet- 
tard). In Trichomanes and Hymenophyllum the thecae are 
seated within the dilated cup-like extremities of the lobes of 
the frond, and are attached to the vein which passes through 
their axis, which is then called their receptacle. In another 
tribe, called GleichenecB, the thecae have a transverse complete, 
instead of a vertical incomplete ring, and they are nearly 
destitute of stalks ; in a third tribe the sori occupy the whole 
of the under surface of the leaf, which becomes contracted, and 
wholly alters its appearance : the thecae have no ring, and the 
cellular tissue of their membrane is not reticulated, but ra- 
diates regularly from the apex. 
In these plants it has been in vain endeavoured to discover 
traces of organs of fecundation. Nevertheless, as it was diffi- 
cult for sexualists to believe that plants of so large a size were 
destitute of such organs, it has been considered indispensable 
that they should be found ; and, accordingly, while all seem 
to agree in considering the thecae as female organs, a variety 
of other parts have been dignified by the title of male organs : 
thus, Micheli and Hedwig found the latter in certain stipitate 
glands of the leaf; Staehelin, Hill, and Schmidel, in the 
elastic ring ; Koelreuter, in the indusium ; Gleichen, in the 
