(40 



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 



