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 Phleospora, 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 orin part zones of the thallus. In Striarta 
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 Gvraudia) two kinds of 
plurilocular sporangia. The one kind are simply 
