Acetabularia is a genus unicellular or single-celled green algae belonging to the family Polyphysaceae which are found in subtropical waters.
They are gigantic in size and complex in form, therefore, used in experiments in cell biology.
Hammerling's nucleocytoplasmic experiments state that the cytoplasm is the centre for all the metabolic activities in the cell and the nucleus is the controlling centre.
So, the correct answer is 'Unicellular uninucleate green alga'.
Hammerling's experiments on Acetobularia involved exchanging
Acetabularia cell is composed of three segments: the "rhizoid" or base which contains the nucleus, the "stalk," and the "cap."
In his experiments, Hammerling grafted the stalk of one species of Acetabularia onto the rhizoid of another species. In all cases, the cap that eventually developed on the grafted cell matched the species of the rhizoid rather than that of the stalk.
This experiment shows that the base is responsible for the type of cap that grows. The nucleus that contains genetic information is in the base, so the nucleus directs cellular development.