How Cultures Are Started 123 



carefully cut or torn out of this sterile surface 

 using sterile instruments and are transferred to 

 nutrient solution, preferably to a semi-solid sub- 

 stratum (Fig. 37). Such fragments should be 

 quite sterile. Cultures of this sort have been pre- 

 pared from willow, poplar, beech, oak, pine, and 

 other trees. Gautheret's most successful cultures 

 were of cambium from Salix capraea (Gautheret, 

 1935, 15, 1937, 68, 1938, 69 ) . The growth obtained 

 is of a loose, fungoid character and in general de- 

 velops rather slowly (Figs. 38, 39). 



Procambial strands. The procedure to be used 

 in isolating procambial strands for cultivation is 

 somewhat similar to that employed with cambium 

 (White, 1939, 78). This tissue can, of course, be 

 most easily removed from stems of succulent indi- 

 viduals. Rapidly growing tips of tobacco, squash, 

 sunflower, and similar plants make excellent mate- 

 rial. Terminal pieces about 8 to 10 inches long 

 are severed and the leaves carefully removed with 

 a sharp scalpel or razor, leaving as little stub as 

 possible. Under aseptic conditions, the epidermis 

 of the distal 1 or 2 inches is stripped off, begin- 

 ning from the proximal end and taking care that 

 the exposed surfaces are not touched by unsterile 

 instruments or epidermis fragments. When the 

 terminal portion is completely exposed, the grow- 

 ing point is grasped with sterile forceps and bent 



