WHAT CONSTITUTES A FERN. 



are produced on the outsides of the pots than on the surface of the mould within 

 them. 



The growth of a fern spore into a fern proceeds as follows : When a spore 

 lights upon a suitable substance, it begins to grow, just as the germ of a flower would 

 do while attached to its parent plant, by assuming a green tint, and producing fresh 

 cells connected with itself and with each other, which in turn produce other similar 

 cells, till at length a little green scale-like object is fotmed, which is actually a blossom 

 of one petal. This is called a " prothallus" which means first of another. Next a 

 tiny bud appears, which is a female organ ; and then some minute thread-like objects, 

 which are the male organs, around it. These last bend over the female organ and 

 fertilise it ; no doubt by the shedding of pollen, though this is too minute to be detected 

 even with a powerful microscope : and then the bud sends down true roots, and soon 

 afterwards the first tiny fronds spring upwards. Except in the case of a few ferns., 

 which are annuals, and in which the growth is therefore more rapid, the whole process 

 usually occupies from eighteen months to two years ; so that one can easily under- 

 stand that it was not easy to trace it all through and unravel the mystery, particularly 

 as the several organs are so minute and the mode of development was so unusual and 

 unexpected. 



As has been indicated, other plants besides ferns are cryptogams, and it is ne- 

 cessary to distinguish the ferns from these. Plants are divided botanically into three 

 great classes, viz., Exogens, in which branches, leaves, blossoms, and the ultimate 

 fruit proceed from buds growing out of the bark ; Endogens where, as in grasses, 

 cereals, and palms, the growth is from within, each blade or leaf forming, at first, a 

 sheath to protect its successors which originate in the very heart of the plant ; and 

 Acrogens, in which the growth is from the top alone. Ferns belong to this last class 

 only ; but still something more is needed to distinguish them from other acrogenous 

 cryptogams. This is found in the fact that they contain woody fibre, and in the 

 nature and position of their fructification, which consists of capsules (generally 

 spherical, spheroidal, or oval, unless growing so closely together as to press each other 

 out of shape), which contain the spores, and which are placed on the edges or under- 

 side of the fronds. These capsules are sometimes bare and grow either singly or in 

 lines or groups ; or are arranged on or around a kind of stem called a " receptacle," 

 and sometimes protected by coverings of various forms ; and it is according to these 

 circumstances, and the manner in which the capsules open when ripe to shed their 

 spores-, that the various tribes and genera of ferns are classed. 



