Filter Paper Raft Nurse Tissue Techniques - Single cells are placed on small pieces (8 x 8 mm) of filter paper (sterilized), which themselves are placed on top of established callus cultures several days in advance. This allows the filter papers to be wetted by the exudates from callus tissues.

The single cells placed on the filter papers derive their nutrition from the callus exudates diffusing through the filters. The cells divide and form macroscopic colonies on the filters; the colonies are isolated and cultured.