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, Avhich 

 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 palese 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 Polypodium pro- 



