User blog comment:Hyp cos/SCG(n) and some related/@comment-11227630-20140810103717

To Wythagoras: The valence-5 vertex is just a symbol for the "root". You can see another graph with high level as a root of lower level rooted graphs.

To LittlePeng9: The rooted graph is useful when eveluating the level of such a graph: a lower-leveled graph connected to somewhere of a higher-leveled graph by one edge.