190 



alburnum and cambium, which rested on the four pillars 

 of dead wood, now simply acting as supports. During the 



Fig. 1. Fig. 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 



