SPORES AND THALLIDIA. 



the Greek, and signifies etymologically precisely the same as "seed", and spores 

 were considered to be peculiar seeds, formed by means of some mysterious processes 

 of fructification. As late as fifty years ago the spore was defined as "that part 

 of a cryptogamic plant which corresponds to the seed, and from which, although 

 it contains no germ, a new plant can be developed ". 



The mode of fructification in the Fern, and, in general, the entire history of its 

 development, were discovered for the first time in 1848. It was then shown that 

 these plants pass through two kinds of regularly alternating generations. One of 

 these is itself inconspicuous, but bears reproductive organs and produces fruits; 

 the other, springing from the fruit, which continues its connection with the parent- 

 plant, is distinguished by fronds and produces spores. Thus the fronds of Ferns 

 bear no sexual reproductive organs, and the spores formed upon them cannot there- 

 fore be looked upon as fruits or even as seeds, a seed being part of a fruit. 



Some people, it is true, treat the entire frond-bearing Fern-plant as a fruit and 

 the spores on the fronds as part of this fruit, although such a theory involves the 

 admission that fruits may strike root, multiply by means of runners and continue 

 to grow for many years, putting forth annually new spore-bearing fronds. Accord- 

 ing to this view, which I cannot endorse, a gigantic tree-fern, aged a hundred years, 

 would be a fruit, and to be consistent it would be necessary to regard a whole 

 grove of Horse-tails as belonging to one single fruit. Other botanists, whilst deny- 

 ing that the Fern-plant with its roots and fronds is the fruit itself, are yet of 

 opinion that the formation of spores in the Fern is a consequence of the process of 

 fruiting, inasmuch as the Fern-plant would never make its appearance at all but for 

 the formation of fruit by the previous generation; and they hold that the spores of 

 Ferns, and of their allies the Horse-tails and Club-mosses, should on that account 

 be distinguished from those of other Cryptogams. To this view there are two 

 objections. In the first place, we know many cases wherein a Fern-plant with 

 spore-bearing fronds is developed from the first generation without any formation 

 of fruit having taken place, and the plant in these instances is in no way different 

 from those which have sprung from fruits of the first generation. Secondly, it is 

 difficult to see why the sporogenous generation should be more dependent on the 

 fruit of the first generation in the case of Ferns than in many other Cryptogams, 

 which similarly exhibit an alternation of generations. 



As the spores of Ferns, and of Cryptogams in general, are not the direct result 

 of a process of fertilization, they are not parts of fruit, but are brood-bodies. They 

 should be placed by the side of the bud forms of brood-body presently to be 

 described, though differing from these in that they always produce a single layer 

 (i.e. a thallus) only, and never a leafy, axial structure. They are just as characteristic 

 of Cryptogams as buds are of Phanerogams or Flowering Plants, and as the name 

 of Cryptogam is no longer quite appropriate, it is often replaced by the term 

 "sporogenous plant". Before the discovery of the alternation of generations in 

 Cryptogams, the name spore was applied to many fruits and rudiments of fruits, 

 particularly where these happened to be unicellular, an error which we should be 



