ALG 
67 
with the other Algz. They include by far the largest 
of the sea-weeds, and are familiar objects of the sea- 
shore. With the exception of 
a few forms like the gulf-weed 
(Sargassum), which seems to be 
really a floating plant, they are 
usually firmly attached to rocks 
and other objects by means of 
highly developed root-like or- 
gans or holdfasts. They may 
grow where they are completely 
submerged, but many of them 
occur between tide-marks so 
that they are partially or com- 
pletely exposed at low tide. A 
common feature of many of 
them is the development of 
floats, or air-bladders by which 
the plant is buoyed up and 
brought near the surface and 
thus exposed to the light. 
Within this class there is 
great range of structure as well 
as size. The simplest forms are 
delicate, branching filaments 
much like many Confervacee, 
except for their brown color. 
Fie. 16.— Ectocarpus granu- 
losus, one of the simpler 
Brown Algz or Pheophycee ; 
A, part of a plant showing 
the sporangia, sp; B, a uni- 
locular sporangium, sp, more 
highly magnified; C, young; 
D, older plurilocular spo- 
rangium; ci, the irregular 
chromatophores; E, a single 
gamete of £. Siliculosus, 
showing the lateral position 
of the cilia. (Fig. E after 
Berthold.) 
Others are gigantic plants reaching a length of a hun- 
dred metres or more, rivalling the largest of terrestrial 
plants. 
As might be expected, these giant kelps show 
a considerable degree of specialization in their tissues, 
but there is to be found almost every intermediate con- 
