The foot by which it is attached often sends out root-like processes - the hydrorhiza (c).
The perisarc when, present invests the hydrorhiza and hydrocaulus; it may stop short below the hydranth, or it may extend farther.
As a general rule polyp-buds are produced from the hydrorhiza and hydrocaulus, while medusa-buds are formed on the hydranth.
In the first place, buds may be produced only from the hydrorhiza, which grows out and branches to form a basal stolon, typically net-like, spreading over the substratum to which the founderpolyp attached itself.
In massive colonies of this kind no sharp distinction can be drawn between hydrorhiza and hydro-, .
