INTRODUCTION. 11 



sporas, are either enclosed in spore cavities (concepta- 

 cles), or arranged externally, singly or in groups (sori). 

 The details of this part of the subject will be given in 

 the description of the Orders and genera. 



The origin of the antheridia is very similar to that of 

 the spores. Both spring from and among the parane- 

 mata, and sometimes grow side by side in the same con- 

 ceptacle. The subsequent development of the antheri- 

 dium is, however,, different. In the place of the spore 

 and perispore, a large transparent closed cell, filled with 

 a number of very minute bodies [sporidia) is formed. 

 These sporidia are analogous to the pollen of flowering 

 plants; but it is not yet decided whether they perform 

 the same fertilizing functions. Some writers, the ma- 

 jority, I think, are of opinion that they do, whilst 

 others maintain that they are only gemmules, and them- 

 selves capable of germination. Without attempting to 

 decide where doctors differ, I will again transcribe from 

 Professor Harvey the following interesting account of 

 them : — " They (the antheridia) are oval, somewhat 

 pointed at one end, and contain a reddish-orange gra- 

 nule; and they are furnished with two extremely slen- 

 der vibratile hairs, or cilia, one of which issues from the 

 narrow extremity of the corpuscle; the other, which is 

 of greater length, from the coloured granule. The 

 corpuscles, at first contained within the antheridium, 

 at length issue from it, escaping into the surrounding- 

 water, and immediately commence a succession of rapid 

 movements to and fro, and in circles and curved lines, 

 strikingly similar to the ciliary movements of some of 

 the Infusoria, or of the spores [zoospores) of some of 

 the freshwater Algae of the Green series. These move- 

 ments depend on the rapid vibrations of the cilia. Du- 



