92 The Ohio Journal of Science [Vol. XX, No. 4, 



for a short time in the morning and again in the late afternoon. 

 In October, burr marigold {Bidens laevis Linnaeus) grew 

 plentifully along the water's edge; this disappeared when the 

 cold weather came on. Duckweed {Lemna trisulca Linnaeus) 

 forined a compact green mat over the surface of the water at 

 several places along the edge; it was present throughout the 

 winter, but became scanty when ice formed on the lake. Several 

 plants of the water hyacinth {Eichornia sp.) floated in this pond. 

 Minnows {Lepomis pallidiis (Mitchill) swarmed here during 

 the fall; large water beetles (Dytiscus) were numerous; and 

 many water striders {Gerris) scampered on the surface of the 

 water. 



Weather conditions affected the appearance of the water 

 in the smaller pond considerably. In the early part of October 

 when the study was begun, most of the water was bright green 

 in color, due to the extreme abundance of the flagellate Carteria 

 multifilis. This organism became active when the sun shone 

 upon the pond, but settled to the bottom and made a thick green 

 sediment on the leaves when the water was shaded from the 

 sun. Late in October after a heavy storm the organism 

 disappeared. For two months during the winter a heavy sheet 

 of ice covered this part' of Mirror Lake. 



The larger pond is at most about 350 feet long (from north- 

 east to south-west) and 116 feet wide (from north-west to south- 

 east). The average depth of water is between two and two and 

 one-half feet. A large spring (J) just north of the eastern end 

 of the larger pond is its largest source of water. In addition, 

 drainage water from the surrounding slopes, occasionally water 

 from the smaller pond, and probably water from small springs 

 in the lake bed help supply this part of Mirror Lake. The 

 water of the large spring bubbles into a cement bowl, which is 

 set in the cement walk. It overflows into a small gutter which 

 carries the water to the lake, about six feet distant. The shore 

 at this point is covered with large boulders, the submerged 

 part of which is covered by algae (mostly Spirogyra). The 

 bottom here is sandy; at the point of inflow from the smaller 

 pond it is covered by a thick layer of fine black sediment ; while 

 in the remainder, small stones, some dead leaves, greenish brown 

 sediment, and algae cover the bottom. The outlet of this 

 pond is through a six-inch pipe at the southwest end; the 



