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very delicate, in fact some are so fragile that a mere breath 
of air will ruin them. 
Following the slime-moulds stand the cases devoted to 
the algae or seaweeds (cases 2 to 16), which may be briefly 
defined as thallophytes with chlorophyl, the green coloring 
matter of plants. The plants of this series are much more 
variable in form than those of the preceding, and are also 
much more numerous. Some forms are microscopic, 
others attain considerable size. The first case of the series 
is occupied by representatives of the blue-green algae 
(case 2) and the diatoms. The plants of these two groups 
are minute, so much so that in most cases the individuals 
can be well seen only with the aid of a microscope. As one 
finds them in nature they commonly form slimy or oozy 
masses which are not particularly attractive to the naked 
eye, but under a compound microscope they are of very 
great interest. Following the series just mentioned are 
the green seaweeds (case 3), the group which includes the 
plants that are sometimes called the pond-scums, green 
slimes, green felts, and stoneworts. Some of these are 
microscopic; however, some of the green seaweeds attain a 
considerable size and begin to look a little more like what 
are popularly termed “‘plants.” After the green seaweeds 
come the brown ones (cases 4 to 8), and here the largest 
kinds are included. In their tissues is found a brownish 
pigment which obscures their green coloring matter. To 
this group belong the widely distributed “‘gulf-weed” or 
““sargasso-weed” (Sargassum) and the gigantic “great 
kelp” of the Pacific Ocean, which sometimes attain a length 
of more than a hundred feet. The seaweeds culminate in 
the red algae, a group in which the plants show some shade 
of red, pink, or purple; these (cases 9 to 16) exhibit a 
marvelous range of form and color. The last group of 
cases containing this series is given to the group of red 
algae which are known as the corallines, on account of 
their outward resemblance to the corals. These plants 
are thoroughly permeated with lime and are often as hard 
