(137) 
as a group perhaps attract the attention of a greater number 
of people than any other group of plants. However, associ- 
ated with what are usually known as ferns are the fern-allies, 
for example the ‘horse-tails” (Hguzsetum), ‘‘lycopods” 
(Lycopodium) and ‘* quillworts” (Zsve¢es), 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 under- 
ground, horizontal 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 (horse-tails). 
he flowering plants (cases 56 to 128) comprise a single 
subkingdom, the Spermatophyta or seed-bearing ‘plants. 
This extensive group seems to have followed two independ- 
ent 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 isa 
comparatively small group, but exhibits great diversity, in- 
cluding plants ranging from straggling shrubs or vines to the 
largest trees. The leaves, too, vary from structures resem- 
bling 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 spermatophytes largely predominates ; 
namely, the angiosperms, fruit-bearing plants, or plants in 
which the seed is borne in a seed-case. These plants also 
existed in the later geological ages, and now form the most 
important and conspicuous part of the vegetation of the earth. 
The fruit-bearing plants (cases 59 to 128) fall into two divis- 
ions, the one in which the seed contains a single leaf, the 
monocotyledons (case §9 to 71); the other in which the seed 
contains two leaves, the dicotyledons (cases 72 to 128). 
