ALGAE — MEIER 415 



dripping rocks among the stalactites and stalagmites in the dark 

 caverns at Liiray, in the Blue Ridge Mountains of Virginia. There 

 is an abundance of calcium carbonates there for the nutrition of 

 these algae. The only light that they receive is occasionally when 

 electric lights are turned on for a short time each day as visitors 

 pass through the caverns. 



The algae that grow in the soil act as agents for the transforma- 

 tion of the ammoniacal substances already present into more com- 

 plex organic substances. They thus aid in bringing about the 

 nitrogen cycle of the soil and in keeping up the gas balance. By 

 their death, the algae contribute largely to the fertility of soils in 

 that they present quantities of organic material to putrefactive bac- 

 teria for decomposition. They are also a source of food for Protozoa 

 and worms. The mucous vestments that encase so many of the soil 

 algae help the soil to retain its moisture. The subterranean algal 

 flora is generally restricted to the upper 18 inches of the soil, al- 

 though algae have been found at a depth of 8 feet below the surface. 



AQUATIC ALGAE 



Aquatic algae of fresh-water habit are of four general types, 

 corresponding to the following habitats: Bogs and swamps, pools 

 and ditches, ponds and lakes, and flowing waters. The algal flora 

 growing in gelatinous masses on submerged plants and in the water 

 of bogs and swamps is varied and rich in quantity. A drop of bog 

 or swamp water when examined under the microscope reveals a 

 fairy-like world of beautiful colors and curious forms. There appear 

 miniature spheres colored different shades of green, yellow, gold, 

 brown, and blue-green; sometimes there appear globes that are 

 massed together or enclosed in gelatinous envelopes, little green new 

 moons arranged singly and in clusters, tiny nets of green, fantas- 

 tically shaped accordions, small green clubs sometimes joined together 

 end to end like pieces of iron on the end of a magnet, little green 

 stars, and minute masses and balls that seem spiked in all directions 

 with bristles like a pincushion full of pins. In and about the drop, 

 like the background of a tapestry, are beautiful straight, twisted, 

 coiled, and spiral green and yellow threads. The whole drop seems 

 to be in motion as the different forms dart quickly, glide gracefully 

 and slowly, or jerk about in the water. Some of the balls seem to 

 explode before the eye, releasing in all directions their diminutive 

 green replicas. 



Many species, such as OphiocytiuTn which, like Proteus, is noted 

 for its gift of transformation, flourish best in rain pools that be- 

 come stagnant and foul in hot weather. They prosper when there 

 is little aeration of the water. TJlothnx idiospora and Tribonema 



