54 PL AST STUDIES 
A. Stems 'bearing foliage leaves 
42. General character. As the purpose of this stem is to 
display foliage leaves, and as it has been discovered that the 
essential life-relation of foliage leaves is the light-relation, 
it follows that a stem of this type must be able to relate its 
leaves to light. It is, therefore, commonly aerial, and that 
it may properly display the leaves it is generally elongated, 
with its joints (nodes) bearing the leaves well separated (see 
Figs. 1, 4, 18, 20). 
The foliage-bearing stem is generally the most conspicu- 
ous part of the plant and gives style to the whole body. 
One's impression of the forms of most plants is obtained 
from the foliage-bearing stems. Such stems have great 
range in size and length of life, from minute size and very 
short life to huge trees which may endure for centuries. 
Branching is also quite a feature of foliage-bearing stems ; 
and when it occurs it is evident that the power of display- 
ing foliage is correspondingly increased. Certain promi- 
nent types of foliage-bearing stems may be considered. 
43. The subterranean type, It may seem strange to in- 
clude any subterranean stem with those that bear foliage, 
as such a stem seems to be away from any light-relation. 
Ordinarily subterranean stems send foliage-bearing branches 
above the surface, and such stems are not to be classed as 
foliage-bearing stems. But often the only stem possessed 
by the plant is subterranean, and no branches are sent to 
the surface. In such cases only foliage leaves appear above 
ground, and they come directly from the subterranean stem. 
The ordinary ferns furnish a conspicuous illustration of 
this habit, all that is seen of them above ground being the 
characteristic leaves, the commonly called "stem" being 
only the petiole of the leaf (see Figs. 45, 46, 144). Many 
seed plants can also be found which show the same habit, 
especially those which flower early in the spring. This 
cannot be regarded as a very favorable type of stem for 
