238 GELIDIACEJE. PART 11, 



This plant is so like the Furcellaria fastigiata (fig. 23 B), 

 that it affords a remarkable instance of similarity of 

 form and total diversity of fructification, not only in 

 the spores and their arrangements, but in the form of 

 the tetraspores ; for in the Polyides they are formed 

 by two sections, one vertical and the other horizontal, 

 while in the Furcellaria the endochrome is divided by 

 three annular sections, as in fig. 23 E. 



The Gelidium corneum, common in Britain and 

 almost everywhere, representing the group Gelidiacese, 

 is opaque, firm, and of a dark purple. The axis with 

 its alternate and repeated branches lying all in one 

 plane, is composed of confervoid threads. This plant 

 is distinguished by having its spore-cases or nuclei 

 divided into two chambers by a fibro-cellular substance ; 

 the spores are either attached to this or to a network 

 of threads ; these bodies and the tetraspores are lodged 

 in the tips of the branchlets. It is one of the most 

 variable of all Algse. 



The Sphserococcoidese comprise some of the most 

 common and beautiful Algse, remarkable for their bril- 

 liant rose and purple tints. This section consists of 

 those red Algse which have their nuclei lodged in an ex- 

 ternal subglobose conceptacle, the spores being formed 

 at the tips of jointed threads rising from a substance 

 at the base of the nucleus. A portion of a nucleus of 

 Sphserococcus coronopifolius, and a single spore magni- 

 fied, is shown at fig. 26 6. The tetraspores are variously 

 disposed. The fronds in this family are either gristly or 

 membranaceous, and totally different from those which 

 follow. They often assume a leafy aspect from the 

 regularity of the nerves, which sometimes perform 

 the functions of a stem when the membraneous 

 border has decayed, and then they give rise in turn 

 to new fronds. That happens in some species of 

 Nitophyllum : a very short stem rises from a minute 



