12 JOURNAL OF THE [January, 



rocks, stone, brickwork and mortar which are porous or hygro- 

 scopic, the Protococcus grows in greater or less abundance, and in 

 walking through the cross-streets of the city, one cannot fail to 

 notice it on the basement steps and railings on the south side of 

 the street, in contrast to its absence on the north. By helping 

 to retain moisture, great aid is given to the disintegration of the 

 rocks and stone work, especially by the dissolving power and 

 then the freezing of the absorbed water. Under some of the 

 flakes which came off from the obelisk, I found an abundance of 

 one and two cells of the genus Protococcus^ the germs of which 

 must have passed through the small exterior cracks and crevices 

 with the rain water: these had only two divisions instead of four 

 as found in P. viridis. Several other cells and spores were found, 

 some of which had been probably imported. If the cells of Proto- 

 coccus formed and subdivided under the flakes, then the growth 

 of chloro-plastids took place in translucent light. They were light 

 yellow green, which became blue green upon wetting, and expo- 

 sure to sunlight. On the duramen of soft woods, after sufficient 

 exposure to soften the fibres, forming lint, P. viridis will grow 

 readily. Its appearance on white cedar trees is usually the first 

 evidence of their softening. The effect of reagents upon the 

 cells is very interesting : concentrated ammonia swells them out 

 nicely for examination — many of the specimens here are mounted 

 in that medium. Caustic potash is more severe, and changes the 

 green color. Alcohol contracts the protoplasmic contents. Hy- 

 drochloric acid changes the green cells to more of a yellow, and 

 shows the cellulose wall plainly. Iodine solution colors them 

 brown, showing the chloro-plastids, and the contents in the hypha. 

 The indications of starch grains are too much obscured by the 

 iodine to be traced, without special treatment. Sulphuric acid 

 added to iodine, colors the cell walls blue in most cases, show- 

 ing that it is cellulose. In fresh growing specimens the sur- 

 rounding gelatinous matter will be colored blue, showing that it 

 is at first cellulose, but later undergoes mucilaginous transforma- 

 tion so as to be no longer recognized as cellulose. I have here 

 some alcoholic extracts of the chlorophyll; cold alcohol does not 

 extract the color quickly, and must be boiled for two or three 

 minutes — add benzine to the product, gently shaking it, let it 

 stand a moment — the benzine has dissolved the dark blue green 



