204. MISSOURI BOTANICAL GARDEN. 
plants in a body of water may diminish or deplete the supply 
of COz and increase the oxygen content beyond saturation. 
8. In the absence of free CO2 the plants may utilize the 
half-bound COs2 of the dissolved bicarbonates, chiefly those of 
calcium and magnesium. 
9. The process of photosynthesis may be so vigorous as to 
exhaust the half-bound COz and render the water alkaline. 
By respiration and absorption of COz from the air more bi- 
carbonates may be formed. This serves as a mechanism for 
the conservation of COz. 
10. Waters rich in lime-carbonates are also rich in vegeta- 
tion. Bog waters, containing humic acids, and, consequently, 
poor in carbonates of lime, are known to be poor in vegetation. 
11. Stagnant water, on account of the large amount of 
COz and the small amount of oxygen, favors the formation of 
colonies and filaments rather than of free individual cells. 
12. Colonies and filamentous forms may be produced ar- 
tificially with some plants, by increasing the amount of CO2 
or diminishing the amount of oxygen in the culture solutions. 
13. Narrow, much-branched filaments are adapted to and 
produced by poorly aérated waters. 
14, Aération, or abundance of oxygen, apparently favors 
the formation of chlorophyll; and alge are brighter green 
when well aérated. 
15. The periodicity of spore formation is not readily in- 
fluenced by aération or gas content of the water. It seems to 
be more a matter of heredity. 
BIBLIOGRAPHY. 
Andrews, F. M. (’05). The effect of gases on nuclear divi- 
sion. Ann. Bot. 19: 522-5380. 1905. 
Angelstein, Udo. (’10). Ueber die Kohlensiureassimilation 
submersed Wasserpflanzen in Bikarbonat-und Karbon- 
atlésungen. Beitrige z. Biol. d. Pflanzen 10: 87-117. 
1910. 
Baldwin, H. B. and Whipple, G. C. (’06). Observed rela- 
tions between carbonic acid and alge growths in Wee- 
quahic Lake, N. J. Rept. Am. Pub. Health. 32: 167- 
182. 1906. 
