THE LIFE -HISTORY OF PLANTS. 



119 



domain of practical cultivation, and the object of the 

 gardener is rather to get rid of than to foster them. 

 Speaking generally, they form no exception to the 

 general rule above stated, and so far from being ' ' cryp- 

 togamons," as they were thought to be in Linnseus's 

 time, these so-called Cryptogams have contributed 

 in these later times the largest share to our know- 

 ledge of the process of reproduction. Ferns and 

 flowering plants, however, are more especially the 



geological epochs from that in which we live, and 

 furnishes links that knit together, in one continuous 

 series, groups of plants such as the Pines and Cycads, 

 formerly considered as having no relationship to 

 Ferns or Lycopods, and which link on in their turn to 

 the flowering plants proper ; serving to show that the 

 vegetable world, like the animal, is not so much made 

 up of myriads of detached independent fragments 

 as of one vast group of mutually related elements. 



Pig. 58. — Lower sarface of portion 



of tlie Frond, Male Fern, show- 



' ing the clusters of spore-cases, 



covered by the kidney-shaped 



memhiane. 



Fig. 60. — One 

 Spore - case of 

 ^the Male Fern 

 (magnified). 



Fig. 59.— Portion of lower 

 surface of Frond of Fern, 

 showing the clusters of 

 spore-cases covered by 

 the kidney-shaped mem- 

 brane (magniiied). 



Fig.61.- Spore- 

 case splitting 

 to set free 

 the spores. 



Pig. 62.— Portion of Prothallus of 

 PtffHs serrvXaia (highly magnified) 

 showing globose antheridia and 

 cylindrical archegonia. 



objects of the gardener's attention, and therefore a 

 knowledge of their mode of reproduction is essential. 



Reproduction of Ferns. — And first as to 

 Ferns. Any one who has cultivated Ferns in a 

 damp house must have noticed the small green 

 plates which cover the walls, line the chinks or 

 crannies, or cover the surface of the pots where un- 

 disturbed. Very probably these green scales, if 

 thought of at all, have been set down as "Liver- 

 wort" or "Moss," something objectionable, or at 

 least unworthy of attention. These green plates, 

 however, form one stage in the process of repro- 

 duction of Ferns, and one of immense physiological 

 interest, because it supplies a clue to the ancient 

 history and genealogy of vegetation in different 



Every one who knows Ferns, is familiar with the 

 brown spots on the under surface of the leaves, or 

 fronds, as they are called. Shake the frond, and a 

 brownish dust falls out. The brown spots (Figs. 58, 

 S9) may, by the aid of a. magnifying-glass, be seen 

 to be aggregations of very small helmet-Hke capsules 

 (Figs. 60, 61), often covered by a kidney-shaped 

 membrane, and which split and liberate the contents, 

 the dust aforesaid. 



When looked at with a pocket lens, this dust is 

 seen to be made up of fine grains or cells, which are 

 called "spores." When these spores fall on to 

 a damp surface, after a time they germinate, so that 

 they are frequently mistaken for seeds. Instead, 

 however, of immediately producing a seedling plant 

 as a seed does, each spore produces a flat green plate 



