Understanding the recursive build of trees(data.tree) in R

Question

I am trying to build trees recursively in R using data.tree package. Anyone who is answering please understand recursion below. The code below contains only two levels of recursion. In the second level recursion I printed the tree structure (marked the print statement in my code for reference), it is similar the image below.

After the entire completion of code the tree structure is.

I do not understand how the tree from level-2 recursion perfectly merged with the tree from level-1.

library(data.tree)
library(visNetwork)

recurs=function(i,previous_iteration_tree)
{
  if(i<=6)
  {
    if(i==1)
    {
      tree<-Node$new(i)
      tree$AddChild(i+1)
      tree$AddChild(i+2)
      tree$AddChild(i+3)
      tree$AddChild(i+4)
    }
    if(i==6)
    {
      dummy<-FindNode(previous_iteration_tree,i-4)
      a=dummy$AddChild(i)
      tree=a

      print(tree)#<------------------HERE
      #see the tree here
    }
  }
  else
    return(0)

  recurs(i+5,tree)

  plot(tree)
}

recurs(1,0)

Please help me out in this case!