416 ANNUAL. REPORT SMITHSONIAN INSTITUTION, 19 3 5 



hombycinum are also peculiar in this respect. Some of the most 

 beautiful microscopic species may be found in the dark, dank, rain- 

 covered interiors of funeral urns in cemeteries. 



Inundated rocks in bogs and swamps give more aeration with, at 

 the same time, a maximum of humidity for the growth of many 

 algal forms. 



Some swamps vary in their quantity of water during the year, as 

 in the spring at flood times and again in the smnmer when they 

 may dry out until only small puddles of water are found around 

 the tufts of grass and swamp plants. The algal flora changes often 

 according to the quantity of water present, and in the winter time 

 certain species may be found under the ice. 



Variation in the gases formed in bogs, swamps, and ponds has its 

 effect on the predominance of type of algal flora growing there. 

 Large gelatinous masses of green and brown algal cells are generally 

 formed on the bottom of the pools and then floated up to the top by 

 the oxygen developed during photosynthesis. Less oxygen is, under 

 ordinary conditions, developed by the larger masses of blue-green 

 algae that remain on the bottom during the whole vegetative period. 

 During hot, still, summer weather, when there is little circulation 

 of air about a pond or pool, the carbonic acid manufactured by 

 the bacteria at the bottom of the pond is not equally distributed 

 through the water, thus depriving the algae of their food. The 

 blue-green algae then tend to rise to the top of the pond for better 

 aeration and form a film of green or yellowish-green scum that is 

 commonly known as water bloom or frog spit. 



During one summer at the Weequahic reservation of the Newark 

 park system, in New Jersey, unusuall}'^ large numbers of algae were 

 formed in the lake. One night, all seemed to be serene about the 

 lake, but the next morning at least 15 tons of dead fish had appeared. 

 Bass, roach, sunfish, catfish, suckers, eels, and even a few carp were 

 found floating dead in all parts of the lake, but in especially large 

 numbers near the inflowing brooks. Instinct had evidently driven 

 them to seek fresh water entering the lake. At the clear spring in 

 the center of the lake there were some living fish. For a time the 

 authorities were considerably puzzled over this mystery of the dead 

 fish. Had the lake water been poisoned or dynamited? The re- 

 maining live fish were gulping air at the surface of the lake. Others 

 had died with their mouths open. It was finally agreed that the 

 fish had died of suffocation. There was found to be an insufficient 

 supply of oxygen in the lake. At a depth of 1 or 2 feet there was 

 practically no oxygen. The algae were decaying and settling to the 

 bottom of the lake. 



