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a cup, which contains the sporangia. In some cases, the whole of the sori of 

 each segment are inclosed in a collective indusium, which is formed by the 

 revolute margin of fertile contracted fronds, as in Pteris, while all the margin 

 or lobules of the frond in certain genera, as in Cheilanthes, are changed in 

 texture, forming an accessory indusium, with which the interior lateral 

 attached special indusium is more or less connivent. These differences in the 

 arrangement of the sori and the structure of the indusia are of the greatest 

 importance, as they form the distinctive characters on which the separation 

 of genera of Ferns from one another and their relative position towards 

 each other are based. 



From what precedes it will be seen that the indusium is a membrane, 

 sometimes totally, sometimes partially, covering the sori, which are themselves 

 collections of sporangia ; also that these sporangia — mostly pedicellate, very 

 rarely sessile, in some cases surrounded by an elastic, articulate ring, in other 

 cases perfectly ringless — are the contents of the sporangiferous receptacle, which 

 is the thickened point or lengthened portion of the ultimate veinules. This is 

 most important to bear in mind, as it is from the contents of these sporangia, 

 fertilised in a most peculiar way, that Fern life is generated. 



Ferns are flowerless plants which furnish us with ample means for a very 

 interesting study ; for there are indeed few, if any, more striking subjects in 

 connection with the science of botany than their singular mode of reproduction. 

 As they do not bear any flowers, Ferns have no seeds proper ; these are 

 replaced by spores, which, as we have endeavoured to explain above, are 

 disposed, according to the different genera, in several ways and on various 

 parts of the fronds. The spore, however, differs from the seed proper in not 

 being the product of fertilisation : it is an unfertilised body, by which, in 

 Cryptogams, the species is reproduced through a series of evolutions, and 

 from which, after several transformations, a young plant grows. Some spores 

 are produced sexually, and in that respect resemble the seeds of Phanerogams, 

 or flowering plants, from which, however, they essentially differ in never 

 inclosing an embryo or young plant as the seed does : these spores, in fact, 

 correspond with the embryo itself rather than with the entire seed. Besides 

 these sexual spores, some asexual ones, which may closely resemble them in 

 appearance, are produced by most Cryptogams through a process of budding 

 or cell-division ; but they are often very different, and it frequently happens 



