Labelling dendrogram has issue

Iam trying to label a dendogram, but iam getting confused out put :

    rng default;  % For reproducibility
    X1= [1 1.5 5 3 4 3];
    X2=[ 1 1.5 5 4 4 3.5]
    X=[X1;X2]
    X=X';

   Y = pdist(X)
    squareform(Y)

    tree = linkage(Y)

    [H,T,outperm]=dendrogram(tree);
    set(gca,'TickDir','out','TickLength',[.002 0],'XTickLabel',['a', 'b','c','d','e','f']);

any suggestion please ?

   can we produce a plot for the HC as figure 1 ??