50 Plant Tissue Culture 



Gautheret and Nobecourt (Nobecourt, 1937, 74, 

 1938, 75, 76, 1939, 77), may be considered as "cam- 

 bium" cultures altbougb grown from root cam- 

 bium rather than from stem cambium. 



Terminal meristems are of two types — stem tips 

 and root tips. The plumule taken from the em- 

 bryo is a stem tip and cultures of this region, 

 taken from no matter what age of plant, behave 

 in much the same way. They differentiate into 

 normal organs ; if they become successfully estab- 

 lished, they develop roots and subsequently be- 

 have as entire plants. As grown to date, they 

 thus offer little or no advantage for physiological 

 studies over seedlings derived in the usual way. 

 Hence, although excised stem tips have been 

 grown with some success by Robbins (1922, 57), 

 White (1933, 116), Avery and LaRue (1938, 237), 

 Behre (1929, 275), and others, such cultures have 

 not proved of great value to the tissue culture 

 field and have not been pushed very far. 



Root tips, on the other hand, represent one of 

 the most important types of material for tissue 

 or organ cultures. If the tips of very young roots 

 of any sort, from ungerminated embryos, seed- 

 lings, old root systems, or adventitious roots pro- 

 duced on cuttings, are obtained in an aseptic con- 

 dition and are excised and placed in nutrient solu- 

 tion or on a nutrient substratum, they will, if con- 



