THE SPERMATOPHYTES 445 
DescrIPTION OF THE WHITE Pine TREE (MATURE SPOROPHYTE) 
From an underground spreading root system there arises an 
erect aerial trunk or stem that extends from the ground to the apex 
of the tree, ending ina terminal bud. The trunk rarely exceeds 
3 feet in diameter and 125 feet in height and is averagely 11% to 
ae * ee sith 4 : Siidier ae 
: ‘i : : a : ae persis i 
Fic. 333.—Transverse section of white pine stem of four years’ growth, showing 
cork (a), cortex (6), phloem (c), cambium (d), xylem (e), secretion reservoir ( i, 
pith (g) and medullary-ray (4). (Photomicrograph.) % 16. 
3 feet in diameter and 50 to 90 feet high. At a varying distance 
above the soil, depending upon environal conditions as well as 
the age of plant, whorls of lateral branches (three to seven in a 
whorl) are seen emanating from the trunk, in horizontal fashion, 
at various levels up to near the apex. These become, under 
conditions prevalent when the tree is grown in the open, grad- 
ually shorter until the summit is reached, giving to the crown 
or upper part of the tree the appearance of a pyramid. These 
