122 Plant Tissue Culture 



all the major meristematic regions except the 

 medullary rays perhaps most difficulties in the 

 way of isolating fragments aseptically without too 

 great injury (White, 1931, 32). Most of the work 

 carried out to date on the cultivation of cambium 

 in vitro has been done by Gautheret (Gautheret, 

 1934, 67, 1935, 15, 1937, 68, 1938, 69, 70, 1939, 71, 

 72, 212, 1940, 73; Gioelli, 1937, 291, 1938, 292). 



To isolate a block of cambium, all six faces of 

 the block must be cut, and this must be done with- 

 out carrying contaminating spores from the sur- 

 face of the plant onto the excised fragment. To 

 perform this operation on the cambium of small 

 woody stems would be almost impossible. It can, 

 however, be successfully carried out on large trees. 

 A piece of bark an inch or more square is cut out 

 with a sharp knife or chisel, being careful to cut 

 well into the sap wood (Fig. 36). Gautheret per- 

 formed this operation with carefully sterilized 

 instruments after surface-sterilizing the tree 

 trunk (Gautheret, 1935, 15), but these precautions 

 are not necessary at this stage. The block is 

 placed in a clean container and transferred to the 

 laboratory. There, under aseptic conditions, it is 

 split at the cambium level in such a way that 

 neither instruments nor possibly contaminated 

 tissue surfaces come in contact with the center of 

 the exposed surface. Pieces of cambium are then 



