70 ALGJS. 



a knotty and jointed appearance to the naked eye or 

 under a low power. The globular capsules, orfavel'ke 

 (favus, a honeycomb) , containing the numerous spores, 

 are situated at the ends of the branchlets, and the 

 tetraspores (fig. 11) in twos or threes on the outer 

 margins of them. 



In Cerdmium rubrum, which is also very common, 

 being found attached to stones, rocks, and the larger 

 Algae, the filaments (PL IV. fig. 12) are stouter than 

 in C. nodosumiy branched so as to form tufts from 2 

 to 10 inches long, and their ends forked, with the 

 tips hooked inwards (fig. 14). The central cells of 

 the filaments are large and rounded, and their walls 

 are entirely covered with a layer of very small angular 

 red cells. The globular capsules (fig. 15), orfavella, are 

 situated on the suter surface of the branches, stalked, 

 and supported by 3 or 4 short branchlets. The tetra- 

 spores (fig. 13) are imbedded in the branches, towards 

 the ends. The capsules called favellse differ from 

 the coccidia in the walls being simply membranous, 

 while the walls of the coccidia, like those of the cera- 

 midia, are composed of cells. 



The tetraspores are usually imbedded, among the 

 cells of the superficial layer of the filaments, and are 

 not very easily recognized by an unpractised eye ; it 

 will be observed in the figures that they are some- 

 times cleft horizontally, at others obliquely. 



CONFERVOID'E^E. This Order consists principally of 

 the green freshwater Algae, although some of them 

 are yellowish brown, purple, or red, and some are 

 marine. Their general structure may be best illus- 

 trated by selecting certain common examples from 

 the families composing the order. The families are 

 13 in number. The species which are figured in the 

 plates are found in fresh water, except when other- 

 wise stated. 



CONFERVA'CE^E. On removing some of the soft 

 green matter found adhering to the stems of water- 



