338 Observations on the Germination of Ferns. 
cumbent, one lapping over the other. Some again have both surfaces 
covered with minute pedicellate glands, while in others the glands 
are only found on one side of the frond, and some, as the different 
species of Adiantum, are perfectly smooth and naked. 
When the lobes have attained a certain size, external increase ceases. 
A slight swelling may sometimes be perceived of the cellules lying at 
the bottom of the sinus, and between the bases of the two lobes, which 
are of a large size ; from the lower surface of the space composed 
of these cellules, a number of small fibrils are sent out, which pene- 
trate a short distance into the soil, and supply the whole cellular 
body with nourishment. They are most numerous under what may 
be termed the base of the primary frond, namely, where the lamina 
first begins to widen ; and between this and the bottom of the sinus, 
is the space on which the little knot of cellular matter is elaborat- 
ed, in which the first gyrate frond and the radicle originate. 
The process by which this is produced consists, in the first in- 
stance, in the emission from the lower surface of the above-mention- 
ed cellules of a number of others ; generally much larger in size, of 
an hemispherical form, and proceeding at right angles to the plane 
of the cellules on which they originate. These arise very near to 
one another, and soon unite into a confluent mass, forming a thick 
coating on the surface of the other cellules. From this coating others 
are protruded, which in like manner become confluent, and this cel- 
lular mass, tapering as it accumulates, terminates in a blunt or 
rounded point. 
Previous to the developement of the frond and radicle, a farther 
accumulation takes place at the summit of the cellular knot, which 
now begins to swell out at two opposite points. The form of the 
knots varies in different species. In some it is round or hemisphe- 
rical ; in others nearly flat, and even hollow, in which case the cel- 
lular swelling is on the upper surface (sometimes but very rarely 
the knot itself is produced on the upper surface ;) some again are 
surrounded by short detached filamentous processes, originating on 
their surface, and composed of elongated almost colourless cellules. 
These are the incipient paleae or scales which surround the caudex 
of some ferns in a more advanced state; in some species, indeed, they 
assume the characters of flat tapering incurvate membranous paleae 
even before the gyrate frond is developed. 
There is a remarkable similarity in the appearance of the cellu- 
lar knot at this stage of its growth, to the formation of the gemmae 
or buds produced in the axillae of the leaflets, and on the surface 
and the margin of the fronds of some ferns, such as Polypodiurn pro- 
