190 
alburnum and cambium, which rested on the four pillars 
of dead wood, now simply acting as supports. During the 
Fie. 1. Fic. 2. 
spring of 1839, I had one of the pillars laid bare (Fig. 1, A), 
thus confining the life-supporting action to the remaining three. 
In a short time afterwards, granulated masses of cellular tissue 
began to form on the upper lip of the incision made, and con- 
tinued to extend down the surface of the bare pillar throughout 
the summer, whilst the lower lip of the incision remained free 
from wood-formation. The woody matter continued to in- 
crease rapidly through the summer of 1840, extending itself 
both in perpendicular and lateral directions from the upper lip. 
On the lower lip two leaf-buds were formed (Fig. 2, C), which 
produced young shoots, when woody matter began to form at 
the bases of these shoots; but on their being removed, the 
farther increase of tissue at once stopped. In May, 1841, the 
masses of cellular tissue and wood had extended from the 
upper lip so as to touch the lower, and to spread along its sur- 
face. 
‘* When the junction took place, a second of the pillars 
