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- 

 togamous," 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 



Fig. 58.— Lower surface of portion surface of Frond of Fern, 



of the Frond, Male Fern, show- showing the clusters of 



' ing the clusters of sjpore-cases, spore-cases covered by 

 covered by the kidney-shaped the kidney-shaped mem- 

 membrane, brane (magnified). 



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. 



Fig.61.- Spore- Fig. 62.— Portion of Prothallus of 



case splitting Pteris serrulata (highly magnified) 



to set free showing globose antlieridia and 



the spores. 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. Auy one who has cultivated Ferns in a 

 damp house must have noticed the small green 

 plates which cover the walls, line the chinks or 

 •rannies, 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- 

 Avort" 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, 

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

 to be aggregations of very small helmet-like 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 plat:^ 



