276 THE AMERICAN MONTHLY 1 Aa 



t) • 



ing Pasteur's fluid iu which the eonidia of Penicillium have 

 been sown at different times. Compare them with a ves- 

 sel in which eonidia have been sown merely in water. 

 Note the white spots, colonies, which appear on the sur- 

 face of Pasteur's fluid, their daily increase in diameter, 

 the appearance of a greenish spot in the centre of each 

 and its increase in size ; the fusion of the colonies as 

 they reach eacli other to form a mat, mT/celium, gradually 

 growing denser and completely covering the culture fluid; 

 the formation on older mycelia of a greenish dust, co7ii- 

 dia, which can easily be blown into air. Note tliat the 

 color is a bluish green, not identical with the color of 

 chlorophyll. 



Mount a very small colony, or a piece cut out of a lar- 

 ger one and examine first uncovered, l. p., you can recog- 

 nize the fine branching fibers, hyphae, of which it is com- 

 posed; some of these stand upright and carry a broom- 

 shaped portion bearing the greenish powdery eonidia. 

 With needles tease the fibres apart, replace the water 

 with 50 per cent alcohol, cover and examine, /i. p., search 

 for single fibres and study them. 31ake an iodine stained 

 mount, and study that in connection, using it for compari- 

 son with the other. Determine first the shapes and posi- 

 tions of the cells. Do you find cross walls? Do the cells 

 branch? At what part of the cell does the branch arise ? 

 Is the cell filled with protoplasm, or are there vacuoles ? 

 Do you find fat droplets^ Can you find any nucleus ? 

 Is there any indication of the presence of chlorophyll ? 

 Is there any indication of a cell-toaU? Study the termin- 

 ation of hyphae and compare them with the older por- 

 tions of the same ? What similarities and differences can 

 you find ? , 



Find the broom-shaped growth at the tips of some of 

 the hyphae, it is the part devoted to the production of 

 eonidia. Locate the string of eonidia. How many are 

 there in a row ? Are all of the same size ? Do the rows 



