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The Myxomycetes or slime-moulds (case 1), standing at 
the bottom of the plant scale, occupy the first exhibition case 
placed at the right hand side of the stairway from the main 
floor. They are thallophytes having neither chlorophyl 
nor (in their vegetative condition) a cell-wall. These very 
simply constituted plants usually grow upon and derive their 
nourishment from decaying organic substances. They vary 
greatly in size, some being exceedingly minute, others assum- 
ing the form of relatively large irregularly shaped masses 
spreading in all directions as they grow. Most of the plants 
are small, and the structure is 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 de- 
fined 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 occu- 
pied by representatives of the blue-green algae (case 2) and 
the diatoms. e plants of these two groups are minute, so 
much so that in most cases the individuals can be well scen 
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 com- 
pound microscope they are of very great interest. Follow- 
ing 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 
