848 



in two bark-covered roots of older, woody plants. The same process sets in 

 here as in the union of aerial organs. The bark on the surfaces of contact 

 is sometimes pushed toward the outside, sometimes enclosed like little 

 islands ; the cambium no longer increases where the pressure makes itself 

 felt on the places of contact, but unites from a common layer, enclosing both 

 roots. Each year, when properly nourished, this layer forms new wood 



layers above the place of union. 

 In regard to the anatomical 

 conditions in the coalescence of 

 tree trunks, we will refer to 

 Kiister's different works^ and 

 will mention here only one rare 

 case which we have observed 

 personally. This was found in 

 the Ellguther forest, near Pros- 

 kau, in a pine ; at several places 

 (ju its trunk a second, thinner 

 trunk had grown fast by natural 

 in-arching. 



The base of the weaker 

 tree had been cut off many years 

 before so that the trunk was 

 obliged to draw its nourishment 

 entirely from the older pine. At 

 the time observed, they were 

 perfectly healthy, and formed a 

 common crown; only it seemed 

 to me that the in-arched, root- 

 less trunk bore somewhat 

 shorter needles. 



I possess a piece of the 

 trunk of another pine in which 

 the tip of a branch, possibly five 

 cm. in diameter, had bored into 

 the main axis and there disap- 

 peared entirely. This is an 

 example of so-called "handled 

 trees." 



All processes of this kind 

 arise from the ability of the cambial tissue to form connecting layers between 

 different axes. The processes differ from grafting only in the previous 

 separation of the cambial layers by the bark of the plant parts; these layers 



FiS- -01. Pine iruin tlie Ellguther I'oie.st in 



which one trunk has continued to nourish a 



second, rootless one connected by natural 



grafting-. 



1 Kiister, E., tjber Stammverwachsungen. Jahrb. f. wiss. Bot. Vol. XXXIII, 

 Part 3. — Pathologische Pflanzenanatomie. Jena 1903, Gustav Fischer, p. 173, Section 

 Wound Wood. 



