30 CULTURE METHODS AND TECHNIQUE 



but in the preparation of these more care is necessary for the pre- 

 vention of bacterial contamination. This is one of the most nutri- 

 tious culture media known for fungi in general. String beans may 

 be obtained on the market at almost any season. Celery leaf stalks 

 are a medium rich in nitrates and desirable for some organisms. 

 All of these highly nutritious media are excellent for securing the 

 vegetative growth of an organism, but it is very often the case 

 that with such media fruiting stages are not obtainable. I have 

 almost invariably obtained better fruiting stages by using ordinary 

 corn meal, or maize meal. This can be prepared to advantage in 

 small flasks. The flask is filled with meal to a depth of about two 

 thirds of an inch. This is then wet with water, hot water being 

 preferable, as cold water does not wet it so readily ; and enough 

 water is added to make the meal quite soft, since considerable water 

 will be absorbed during sterilization. Cylinders or plugs of various 

 root crops, or stems of plants, dead wood, and various other products, 

 may serve special purposes. 



In preparing the cylinders of root crops, the roots should be 

 thoroughly washed and pared, and then cut into pieces of desired 

 size. If used in a test tube, a scoop which cuts out a cylindrical 

 piece will be found convenient. These cylindrical plugs, say three 

 inches long, are then cut diagonally. Ordinarily a piece is placed in 

 a test tube of 1 2 1 5 x 1 50 180 mm., and then ^ to I inch of 

 water is added. More desirable for many purposes, and particularly 

 for transportation, is to put in each tube half an inch or so of satu- 

 rated absorbent cotton, and within this rests the end of the nutrient 

 substance, which is thus firmly held in place. The latter method 

 avoids all fluids in the cultures, and the tubes may be inclined or 

 placed upright afterwards, as convenient. In somewhat the same 

 way wads of absorbent cotton or of filter paper may be placed in 

 the tubes, and these wads then moistened or wet with any nutrient 

 solutions desired, and subsequently sterilized. Closely folded pieces 

 of filter paper may be used in this way with solutions of known com- 

 position for very accurate work in nutrition ; and in such cases a 

 supply of the liquid may also be placed in the tube so that the 

 culture may not dry out for a considerable period. 



It is often desirable, and indispensable for the best growth, to 

 use in connection with a culture liquid of known composition some 



