2006 Journal oi' Applied Microscopy 



primary root in a damp chamber until they have attained a length of 5-6 cm. 

 Moisten a piece of blue litmus paper with distilled water and bring it into con- 

 tact with the terminal 2 cm. of the root. A decided acid reaction will be shown. 



3. The Corroding Action of Roots. Another method of demonstrating the 

 corrosive action of roots is by allowing them to grow against marble. Embed a 

 piece of marble with a polished surface about 6 cm. by 10 cm. in the bottom of 

 a crock of sand, incline the polished surface so that the roots growing downward 

 will strike upon it. If the surface of the block shows scratches they should be 

 sketched at the time of making the preparation, and the sketch preserved for 

 reference at the final observation. Plant above the marble seeds of the bean 

 {Phaseolus cotnfnunis), watermelon {Citrullus vulgaris), or Vicia Faba ; when the 

 stems are 2-4 cm. above the surface of the sand, empty out the contents of the 

 jar and examine the corrosion figures on the marble. 



4. Nutrition of Fungi. The elements necessary for the nutrition of fungi 

 may be determined experimentally in the same way as in the case of chlorophyll- 

 bearing plants. It will be noted that the following formula contains all the 

 elements used for the water cultures, with the addition of two organic substances 

 — dextrose and peptone — though not all fungi need both dextrose and peptone. 

 It is more difficult to obtain satisfactory results with cultures of fungi than with 

 those of green plants for two reasons — a slight impurity in the culture solution 

 is not so quickly exhausted as in the cultures of the larger green plants, and 

 many fungi can make considerable though not full growth without the presence 

 of all the mineral substances. Carefully clean and dry a number of 200 c. c. 

 Erlenmeyer flasks ; in each of two flasks place half of the following formula, with 

 such modifications as are necessary to omit one element in turn from each pair 

 of duplicates : 



Dextrose, ------ 5 grams. 



Peptone, 1 gram. 



Ammonium nitrate, ----- 1 " 



Magnesium sulphate, crystals, - - - .25 " 



Potassium monophosphate, - - - .25 " 



Calcium chlorid, ----- .Qi " 



Distilled water, - - - - - 100 c. c. 



The flasks are then closed with firm plugs of cotton-batting, and sterilized in 

 hot steam for 40 to 50 minutes on each of three successive days. When the 

 flasks are cool the culture medium in each is to be inoculated with the spores 

 of Pe-nicilliuni glancum, or of Phycotnyces nitens ; then labelled, stating what was 

 omitted from the culture fluid. Observations should be made each week for 

 three or four weeks. Howard S. Reed. 



University of Micliigan. 



