OEGAXS OF HEPEODrCTIOX. 359 



pollen. It must be noticed, however, that spores, although 

 similar in structure to pollen, perform essentially different func- 

 tions. The threads which are thus produced by the germination 

 of spores, may either reproduce the plant directly, or giye rise to 

 an intermediate body of varying form, called the prothaUium, 

 pro'thallus, ot pro-emhryo ( fig. 787, p), from which the fructiferous 

 or fruit-bearing frond or stem ultimately springs. 



Although Cryptogamous Plants have been thus described 

 above as destitute of an embryo, yet it must be admitted that the 

 spores of some of these plants do contain an analogous body, — 

 that is to say, they contain a body which has all the elements of 

 the future plant in a rudimentary state. Such spores are, how- 

 ever, of but rare occurrence, and the rudimentary plant which 

 they contain is of so different a nature from the true embryo of 

 Phanerogamous Plants, that such exceptional cases can scarcely 

 be said to interfere materially with the character given above. 



Such are the chief distinctive characters in the reproductive 

 organs of Cryptogamous and 'Phanerogamous Plants. The nature 

 of these organs in the different tribes of flowerless plants is, 

 however, so remarkable, that, in order to make ourselves ac- 

 quainted with them, it will be necessary for us to describe the 

 peculiarities of each separately. 



The Cryptogamous Plants have been arranged by botanists 

 in two great divisions, called respectively Acrogens and Thal- 

 logens. The general characters of these will be described here- 

 after, when treating of Systematic Botany ; but it will be better 

 for us to keep these two groups in view in our sketch of the re- 

 productive organs of flowerless plants, and hence we shall treat 

 of them under these two heads. 



Section 1. — EEPRODrcTrvE Oegaxs of Acrogens. 



Acrogenous Plants have been also divide<l into several sub- 

 divisions, called Natural Orders or Families ; thf se are the 

 Filices, Equisetacea, Marsileaeece, Lycopodiaeece, Musci, Hepa- 

 ticacece, and CharacecB. The orderof arrangement of these Natii- 

 ral Orders is differently given by botanists, but as our object is 

 only to give a general sketch of their reproductive organs, we have 

 adopted the above arrangement as perhaps, upon the whole, the 

 simplest, and from its being the one most commonly in use. 

 The general characters of these orders will be described under 

 their respective heads in Systematic Botany ; — the nature of 

 their reproductive organs has now only to be described. 



1. Filices or Feexs. — The fructification of these plants con- 

 sists of little somewhat rounded cases, called eapsides or theccB 

 [fig. 783, sp), springing commonly from the veins on the under 

 surface or back of their leaves or fronds {figs. 783 and 78-i), and 



