260 Palaeontologie. — Algae. 



5. pulcherrbna abgebildeten Exemplare gehören nicht zu der gleichen 

 Art wie die Abbildung von Sauveur. Deshalb war es notwendig, 

 für Stur's und Gothan's Pflanzen einen neuen Namen aufzustellen, 

 wofür 5. pulchrior Gothan et Jongm. nov. nom. gewählt wurde. 



S. {Palmatopteris) pulcherrima Cr^pin wurde auch im nieder- 

 ländischen Carbon angetroffen. Jongmans. 



Chambers, C. O., The relation of algae to dissolved oxy- 

 gen and carbondioxide. With special reference to car- 

 bonates. (Missouri bot. Garden. 23. Ann. Rept. p. 171 — 207.1912.) 



The paper contains a review of the literature on this subject 

 and new investigations. These are summarized as follows: 



There is an intimate and mutual relation between the algae 

 and submerged aquatics in a body of water and the gases dissolved 

 in that water. They fluctuate together. 



Air, or its constituents, oxygen and COj, are as essential to 

 water plants as water is to land plants, and equally difficult to 

 secure. 



Warm and stagnant water is poorer in these essentials than 

 colder water gently agitated by wind or currents. 



Currents are especially beneficial to attached plants by rene- 

 wing or removing these gases. 



Some species demand more aeration than others. Some species 

 are more tolerant of stagnant waters than others. 



Filamentous forms with large cells and thin outer walls are best 

 adapted to stagnant waters. Such forms predominate in warm, tro- 

 pical fresh waters, which are poorly aerated: 



The photosynthesis of rapidly-growing algae and aquatic plants 

 in a body of water may diminish or deplete the supply of CO2 and 

 increase the oxygen content beyond Saturation. 



In the absence of free CO2 the plants may utilize the half-bound 

 CO2 of the dissolved bicarbonates, chiefly those of calcium and 

 magnesium. 



The process of photosynthesis may be so vigorous as to exhaust 

 the halfbound CO2 and render the water alkaline. By respiration 

 and absorption of CO2 from the air more bicarbonates may be for- 

 med. This serves as a mechanism for the conservation of CO2. 



Waters rieh in lime-carbonates are also rieh in Vegetation. Bog 

 waters, containing humic acids, and, consequently, poor in carbo- 

 nates of lime, are known to be poor in Vegetation. 



Stagnant waters, on account of the large amount of CO2 and 

 the small amount of oxygen, favors the formation of colonies and 

 filaments rather than of free individual cells. 



Colonies and filamentous forms may be produced artificially 

 with some plants, by increasing the amount of COo or diminishing 

 the amount of oxygen in the culture Solutions. 



Narrow, much-branched filaments are adapted to and produced 

 by poorly aerated waters. 



Aeration, or abundance of oxygen, apparently favors the for- 

 mation of Chlorophyll; and algae are brighter green, when well 

 aerated. 



The periodicity of spore formation is not readily influenced 

 by aeration or gas content of the water. It seems to be more a 

 matter of heredity. Jongmans. 



