THE FOOD OF PLANTS. 



93 



The surface of the bread, however, soon takes on a greenish 

 coloration due to a vigorous growth of Penicillium crustaceum. 

 Under the microscope we can readily make out the mycelium 

 and also the fertile hyphae, branched in a penicillate manner 

 at their ends, where they bear rows 

 of spores (see Fig. 27). 



If we wish to make culture ex- 

 periments with the Penicillium, 

 we first prepare a solution con- 

 taining in every 100 c.c. of water 

 0'05 gr. Ammonium phosphate 

 (prepared by saturating Phosphoric 

 acid with ammonia, and evapora- 

 ting the solution), 0'05 gr. of acid 

 Potassium phosphate (KH 2 P0 4 ), 

 0'03 gr. of Magnesium sulphate 

 and O'Ol gr. of Calcium chloride. 

 Respecting the addition of an iron 

 salt, see p. 58. To this solution 

 we add the organic substances 

 whose value as nutrient material 

 for the Penicillium we wish to test, 

 together with spores of the fungus. 

 I filled, e.g., four small glasses 

 with 20 c.c. each of the solution. 

 To a nothing was added ; to 6 was 

 added 0"2 gr. of grape sugar; to 

 c, 0'2 gr. of Oxalic acid ; to d 0*2 

 gr. of Citric acid, a and b were 

 acidified by addition of a few 

 drops of very dilute Sulphuric 

 acid. In order to sow minimal 

 quantities of spores, the best plan 

 is to distribute some Penicillium 

 material, grown e.g. on bread, in 



a large quantity of water, and add Gonidiophore with tufts of branches 

 to the food solutions only a few c c 8 ' and *"' basidia ' b; steri * ma ' st: ar \ d 



J "^- gonidia. Magn.540. (After Strasburger.) 



of this water. The culture vessels 



are now covered with glazed paper, and left to themselves in 



darkness at the ordinary temperature. 



In my experiments no Penicillium growth was observable after 



FIG. 27. Penicillium crustaceum 



