232 



CERAMIUM. 



PART II. 



fig. 25 a represents a thread of this plant with tetra- 

 spores, much magnified ; b, a portion of the same, more 

 highly magnified ; c, a thread with naked nuclei, gongy- 

 lospermous, that is, filled with a mass of spores, magni- 

 fied ; and d y a spore, magnified more highly. The nuclei 

 are naked in all the Ceramiacese. 



The genus Ceramium, some species of which have 

 spinulose branchlets, is characterized by the tips of the 



d \* 



Fig. 25. Callithamnion corymbosum. 



forks of its terminal branchlets being hooked inwards, 

 and by the stems and branches being striped by alternate 

 hyaline and coloured bands as in the preceding genus, 

 though the arrangement of the colours is somewhat 

 different. The Ceramium ciliatum, which is a dense 

 tuft of capillary jointed filaments, from two to six inches 

 long, repeatedly and regularly forked, has the tips of 

 the last forks so much hooked inwards, that the ex- 

 tremities of the branchlets look as if they were heart- 

 shaped. It has minute spores in globular nuclei, sessile 



