8 A TEXT-BOOK OF BOTANY. 



SCHIZOPHYCEyE, OR FISSION ALG^.— This group of 

 plants, also known as Cyanophyceae or Blue-green Algae (Fig. 6), 

 are generally found in more or less stagnant water and are charac- 

 terized by having associated with the chlorophyll a definite blue- 

 green principle known as phycocyanin. However, many of these 

 Algae contain other pigments in such quantity as to give them dis- 

 tinct colors much like those found in the red and brown Algae, such 

 as Trichodesmium, a filamentous Alga giving the Red Sea its char- 

 acteristic appearance. Some of these live at the highest tempera- 

 ture known to support life ; some developing, as Gloeocapsa, on the 

 sides of the geysers in the Yellowstone Park. These forms have 

 very wide habits, some living, as Stigonema, in symbiosis with 

 fungi; some, as Nostoc, are endophytic in habit, living in the de- 

 pressions of various plants, and others, as Mastigocoleus, boring 

 into shells. 



They are found mostly in fresh water, and some, as Uroglena, 

 cause considerable trouble in public water supplies by reason of 

 their breaking down the cell-wall and the liberation of a fetid 

 oily substance. 



While these plants do not produce true spores, yet they are 

 able to tide themselves over adverse conditions by producing rest- 

 ing bodies through the formation of a thicker membrane and a 

 more concentrated cell-content. In this condition they are able to 

 hold over for several years and then grow when the conditions of 

 temperature, nutrition, etc., are suitable for their germination. As 

 a rule, they grow best in shallow, stagnant water with the rela- 

 tively high temperature of the summer months. When public 

 water supplies are polluted by these blue-green Algae it has been 

 found that the Algae are completely destroyed by the addition of 

 a very small amount of copper sulphate to the reservoir. As 

 small a quantity as one part per million is sufficient to accomplish 

 this result, not only killing the troublesome organisms, but pre- 

 venting their development for some months to come. A few of 

 the common forms will be considered. 



Gloeocapsa is one of the simplest of the Blue-green Algae 

 (Fig. 6), consisting of spheroidal cells from 0.0035 to 0.005 "^"^• 

 in diameter, of a yellowish or brownish-yellow color, and usually 

 embedded in groups of two or some multiple of four in an olive- 



