132 Plant Tissue Culture 



of these categories in the preliminary attack upon 

 most problems is the first, since for most materials 

 it possesses, of all the methods of approach, the 

 greatest reliability and flexibility. 



Bonner (1940, 201) carries root cultures in Petri 

 dishes, but these seem to the writer of this volume 

 to offer no significant advantages over flasks. Cer- 

 tainly they must be handled with much greater care 

 to avoid slopping, and would seem much more likely 

 to become contaminated. Fell (1928 et seq., 392- 

 401) uses, for animal tissue cultures, shallow ves- 

 sels of the "salt-cellar" or embryological watch 

 glass type placed in Petri dishes acting as moist 

 chambers. These may have distinct advantages 

 for cultures of small volume such as callus cul- 

 tures but cannot be used for roots. 



The preparation of stocks. In any piece of 

 scientific work, one of the prime requisites if sig- 

 nificant results are to be obtained is an adequate 

 supply of uniform, duplicable material with which 

 to work. The tissue culture technique has in this 

 respect one great advantage over most other cul- 

 ture practices — that it permits the building up of 

 vegetatively derived clones, all members derived 

 by division of a single ancestral fragment so that 

 all members have exactly the same genetic consti- 

 tution. The question of genetic uniformity and 

 stability is entirely eliminated. One might expect 



