( 223 ) 
that has recently been burnt over, as species of Funaria 
and Leptobryum, while others grow only on the bones of 
dead animals or in places where animal refuse has accumu- 
lated. 
Next higher in the plant kingdom is the subkingdom 
Pteridophyta, or ferns and fern-allies, the seedless plants 
with roots, stems, leaves, and woody tissue (cases 49 to 
55). The ferns as a group perhaps attract the attention 
of a greater number of people than any other series of 
plants. Associated with what are usually known as ferns 
are the fern-allies, for example the “horse-tails” (E£gui- 
setum), “lycopods” (Lycopodium), and ‘‘quillworts” 
(Isoetes), but these are usually less conspicuous than the 
“ferns.” Fern-plants differ from all the plants of simpler 
organization in having vascular (woody) tissue, that is, 
a system of vessels for conducting sap through the different 
parts of the plant-body. They exhibit an almost infinite 
variety of form; their stems may be underground, hori- 
zontal on the ground, or erect; the leaves are either simple 
or compound, and sometimes perform both the work of 
foliage leaves and that of bearing the spore-cases (ferns), 
while in other cases some of the leaves have become changed 
into mere spore-bearing organs (cinnamon-fern). 
The ‘‘flowering” plants (cases 56 to 128) comprise a 
single subkingdom, the Spermatophyta, or seed-bearing 
plants. This extensive group seems to have followed two 
independent lines of development and consequently the 
plants fall into two well marked groups, the first being 
the gymnosperms, cone-bearing plants, or plants in which 
the seeds are borne exposed in variously shaped cones 
(cases 56 to 58). This is a comparatively small group, 
but exhibits great diversity, including plants ranging from 
straggling shrubs or vines to the largest trees. The leaves, 
too, vary from structures resembling needles or scales to 
expanded fern-like structures of considerable variety. 
In a former geological age these plants were the dominant 
seed-bearing plants, but now the second group of the sper- 
