(1) The purpose of this experiment is to explore whether the shape of umbrella cap is controlled by nucleus or cytoplasm. According to the function of the core, it is assumed that the core controls the shape of the umbrella cap.

(2) The experimental method is to graft the first kind of umbrella stalk on the second kind of artificial root. Since the nucleus of the grafted umbrella comes from the second species, if the umbrella cap of the grafted umbrella is the same as that of the second species, it means that the nucleus controls the shape of the umbrella cap.

(3) There is no control experiment in this experiment. In order to make the experimental results more convincing, we should increase the experiment of grafting the umbrella handle of B on the false root of A and observing the shape of the umbrella cap as a control.

So the answer is:

(1) The nucleus controls the inheritance of cells (umbrella cap shape)

(2) A-shaped umbrella cap grows from B ..

(3) need? Then, the stem of B was grafted on the false root of A, and the shape of the umbrella cap was observed.