Minnesota Plant Life. 



35 



needs of the plant may determine. Because of its rolling habit 

 this little plant is called Volvox, or the rolling alga. 



Flower-pot algae. Somewhat related to the Volvox, but by 

 no means so interesting an object, is the bright-green alga which 

 forms a scurf on flower-pots in green-houses, upon curbstones 

 near hydrants, upon the foundation stones of houses standing 

 upon damp places, upon damp soil, and often upon fallen trees 

 in the deep forest. A microscopic examination of the green 



FIG. 10. Patches of pond-scum floating in a tank. A lime-encrusting alga grows on the 

 boards up to high-water mark. Near Minneapolis. After photograph by Mr. R. W. 

 Squires. 



scurf on a flower-pot would show that it is made up of countless 

 very tiny green spheres, fifty of which could be laid side by 

 side across the dot over a lower case "i" on this page. The way 

 in which these little plants multiply is as follows : While they 

 are finding food in plenty in the moisture about them, the con- 

 tents of each of the spheres will be seen to divide into two, four 

 or eight smaller balls. The membrane of the old sphere then 

 dissolves and the little balls tumble out and grow to the size of 



