30 INTRODUCTION TO BOTANY 
other common plants root readily in water and grow for a 
long time if supplied only with ordinary river or well water. 
The number of kinds of seed plants which float, and therefore 
Fie, 22. Aérial roots (brace roots) of corn. Reduced 
Note that the series a and b began as aérial roots, but later entered the ground 
and then developed many small branches. Those at c, if not checked by frost, 
would eventually also have reached the ground 
