(112) 
The Thallophyta (cases 1 to 40), may be defined as 
plants without true roots, stems, or leaves; but notwith- 
standing their simple structure they exhibit an infinite 
variety of form and color. 
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 sub- 
stances. They vary greatly i in size, some being exceedingly 
minute, others assuming the form of relatively large ir- 
regularly 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 
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 (cases 3 and 4), the group which includes the 
plants that are sometimes called the pond-scums, green 
slimes, green felts, and stoneworts. Some of jee are 
microscopic; however, some of the green seaweeds attain a 
considerable size and begin to look a little more like what 
