102 SEAWEEDS 



cases copiously branched and clothed with hairs 

 (including a terminal one), shows slight differentia- 

 tion of tissues. In the more simple forms an 

 articulated appearance is presented, the upper 

 portions, particularly of the branches, remaining 

 as rows of single cells, while the lower portions con- 

 sist of equal tiers of cells produced by division 

 lengthwise of the original single row. In the 

 more highly differentiated forms this appearance of 

 articulation is lost, since the thallus consists of two 

 tissue layers, a cortical layer of short rectangular 

 cells, and an interior tissue of elongated cells, also 

 rectangular in shape in most cases. In Striaria, 

 however, the cells of the interior tissue are roundish 

 in cross-section, and they line a hollow interior in 

 the fully developed plants. The growth in length is 

 by a subterminal intercalary growing point, but in 

 Kjellmania the cells of the whole thallus participate 

 in this process. In Phlceospora, portions of the shoot- 

 are detached and lead to vegetative propagation. 



The Reproductive Organs. Both unilocular and 

 plurilocular sporangia are, as a rule, the equivalents 

 of superficial cells, and are generally partially 

 immersed in the tissue. They occur in some cases 

 singly, but more frequently in sori or patches cover- 

 ing wholly or in part zones of the thallus. In Striaria 

 paraphyses are produced among the sporangia. Kjell- 

 mania sorifera presents a somewhat aberrant type. 

 Its peculiarity of growth has been mentioned above, 

 and in point of reproduction it presents the further 

 singularity of possessing (like Giraudia) two kinds of 

 plurilocular sporangia. The one kind are simply 



