(27) 



The Myxomycetes or slime-moulds (case i), 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. 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 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 



