382 FERTILIZATION AND DEVELOPMENT OF FERNS. 



cells built-up in layers of four cells each, one upon another, so as 

 to form a kind of chimney or shaft, having a central passage that 

 leads down to the cavity at its base, wherein the Germ-cell (B, a) 

 is contained. Into this cavity the Antherozoids penetrate, so as 

 to come into contact with the Germ-cell ; and, by the softening 

 of the membrane at its apex they are even enabled to enter its 

 cavity, within which a minute Embryonal Corpuscle was previ- 

 ously distinguishable. This corpuscle, when fertilized by the 

 antherozoids which move actively round it, becomes the Primor- 

 dial Cell of a new plant, the development of which speedily com- 

 mences.* By the usual process of binary subdivision a globular 

 homogeneous mass of cells is at first formed ; but rudiments of 

 special organs soon begin to make their appearance ; the Germ 

 grows at the expense of the nutriment prepared for it by the 

 Pro thallium ; and it soon bursts forth from the cavity of thearche- 

 gonium, which organ in the meantime is becoming atrophied. In 

 the very beginning of its development the tendency % seen in the 

 cells of one extremity to grow upwards, so as to evolve the Stem 

 and Leaves, and in those of the other extremity to grow downwards 

 to form the Root ; and when these organs have been sufficiently 

 developed to absorb and prepare the nutriment which the young 



* See Hofmeister, in "Ann. of Nat. Hist.," 2nd Ser., Vol. xiv., p. 272, 

 and his Treatise on the Higher Cryptogarnia, published by the Ray So- 

 ciety. The study of the development of the Spores of Ferns, and of the 

 act of Fertilization and of its products, may be conveniently prosecuted 

 as follows :— Let a Frond of a Fern whose fructification is mature be laid 

 upon a piece of fine paper, with its spore-bearing surface downwards ; in 

 the course of a day or two this paper will be found to be covered with a 

 very fine brownish dust, which consists of the discharged Spores. This 

 must be carefully collected, and should be spread upon the surface of a 

 smoothed fragment of porous sandstone, the stone being placed in a 

 saucer, the bottom of which is covered with water ; and a glass tumbler 

 being inverted over it, the requisite supply of moisture is ensured, and 

 the spores will germinate luxuriantly. Some of the Prothallia soon ad- 

 vance beyond the rest ; and at the time when the advanced ones have 

 long ceased to produce Antheridia, and bear abundance of Archegonia, 

 those which have remained behind in their growth are beginning to be 

 covered with Antheridia. If the crop be now kept with little moisture 

 for several weeks, and then suddenly watered, a large number of An- 

 theridia and Archegonia simultaneously open ; and in a few hours after- 

 wards, the surface of the larger Prothallia will be found almost covered 

 with moving antherozoids. Such Prothallia as exhibit freshly-opened 

 Archegonia are now to be held by one lobe between the forefinger and 

 thumb of the left hand, so that the upper surface of the Prothallium lies 

 upon the thumb ; and th3 thinnest possible sections are then to be made 

 with a thin narrow-bladed knife, perpendicularly to its surface. Of 

 these sections, which, after much practice, may be made no more than 

 l-15th of a line in thickness, some will probably lay open the canals of 

 the Archegonia ; and within these, when examined with a power of 200 

 or 300 diameters, Antherozoids may be occasionally distinguished. The 

 Prothallium of the common Osmunda regalis will be found to afford 

 peculiar facilities for observation of the development of the Antheridia, 

 which are produced at its margin. (See Rev. F. Howlett in " Intellectual 

 Observer," Vol. vii. p. 32). 



