332 MICROSCOPIC STRUCTURE OF HIGHER CRYPTOGAMIA. 



them artificially in Aquaria, it is requisite to protect them from 

 an excess of light ; since otherwise they become unhealthy. The 

 nature of the fructification of the Rhodospermece (or Floridece) is less 

 perfectly understood than that of the Fucoid Algae. It is certain, 

 however, that antheridia exist among them; these being de- 

 veloped in individuals that do not produce spores, and in pretty 

 much the same situations. The products of these antheridia, 

 however, do not exhibit the spontaneous motion of ordinary an- 

 therozoids. Of the spores there are two kinds, of which one set 

 are probably "gemmse," whilst the other are " germ-cells;" but 

 it is not yet determined to which of the two these characters 

 respectively belong. The "tetraspores," which are peculiarly 

 characteristic of the group, being found in every one of its sub- 

 divisions, are usually imbedded in the general substance of the 

 frond, though they sometimes congregate in particular parts, or 

 are restricted to a special branch. Each group (Fig. 117, B) seems 



FIG. 117. 



Arrangement of tretraspores, in Carpocaulon mediterraneum : A, entire plant ; B, longitudinal section 

 of branch. (N. B. Where only three tetraspores are seen, it is merely because the fourth did not hap- 

 pen to be so placed as to be seen at the same view.) 



to be evolved within one of the ordinary cells of the frond, which 

 undergoes a duplicative subdivision ; the four secondary cells, 

 however, remain enclosed within their primary cell until the 

 period of maturity, a new envelope, the "perispore," being 

 formed around them. In the Corallines, which are sea-weeds 

 whose tissue is consolidated by calcareous deposit, the tetra- 

 spores are included within hollow conceptacles ; but generally 

 speaking, it is the simple spores only which are thus specially 



