THE SEED PLANTS 
289 
tissue in the ferns, but in the pines and their relatives the 
vascular tissue is organized into a stem that may attain great 
height and thickness (fig. 222). These plants have been 
highly successful in the struggle for 
light. Such plants also have quite 
extensive woody root systems, which 
serve to anchor these great trees and 
to gather the water and substances 
in solution that are conducted through 
the whole length of the stem to the 
leaves. 
The significance of the stems of 
gymnosperms and some angiosperms 
to those industries that use timber 
is difficult to estimate. Timber is 
used for all sorts of useful and orna- 
mental products, and many kinds of 
industry are dependent upon timber ; 
but it must be remembered that 
woody stems are developed as struc- 
tures which support leaves and con- 
duct food materials to and from them, 
in connection with the plants’ strug- 
gle to live, and that man’s use of 
this timber is, botanically, merely 
incidental. 
274, Pine cones. Two kinds of 
cones are borne upon pines: one is 
the seed-forming cone (fig. 223); the 
other is the staminate cone. The 
seed cone is composed of heavy, leaf- 
like parts, on the upper sides of 
which the developing seeds or ovules 
Fic. 224, Diagram of part of 
a seed cone of a pine, with 
ovules in normal position 
S, sporophylls, or leaf-like parts 
of the cone; O, ovule; J, the 
covering of the ovule, called 
the integument; 7G, the female 
gametophyte, which bears the 
archegonium A, in which the 
egg is formed; Pt, pollen tubes 
from pollen grains which lie 
upon the tip of the ovule 
are formed. Within the ovule the egg is produced (fig. 224). 
The staminate cones appear early in the spring, shed their 
pollen, and soon wither and fall to the ground. These cones 
