Fig. 15.2-10a and b. Transverse and tangential sections of white pine wood. These high magnifications show that circular bordered pits do occasionally occur in the tangential walls of conifer tracheids. But notice that this is in the latewood, produced just before the vascular cambium became dormant during autumn and winter. None is visible in the earlywood at the top of the micrograph of the transverse section. One circular bordered pit occurs on the wall between a latewood tracheid and an earlywood tracheid such a pit is called a growth ring bridge. In the tangential section, it is more obvious that the circular bordered pits in the tangential wall are actually relatively abundant but they are also rather small.