40 PLANT BIOLOGY 



3. Make a diagram greatly enlarged of a piece of root 

 prepared as directed above. Label cortex, central 

 cylinder, fibers of central cylinder. 



B. Root-hairs. 



Note to the Teacher. Root-hairs may be grown for study as 

 follows : Cover the bottom of as many Petri dishes as are needed 

 with a layer of blue blotting paper. Soak the paper with water and 

 lay several grains of soaked barley, oats, or corn upon the bottom 

 of each dish. Put ttte covered dishes in a warm place for several 

 days. When the root- hairs have developed, wipe the moisture from 

 the inside of the covers, quickly replacing the latter. If Petri dishes 

 are not available, two clean glasses of any convenient size may be 

 used instead. Cover one of the plates with layers of wet blotting 

 paper, put the soaked grains in position, and cover with the second 

 glass, fastening the two together with threads or strings. Stand 

 one end of the preparation thus made in a jar with enough water to 

 reach the lower edge of the blotting paper. 



Examine first with the naked eye and then with a hand 

 magnifier the roots of sprouted grains, developed as described 

 above. Notice tiny outgrowths from the sides of the roots; 

 these outgrowths are called root-hairs. 



1. Look at the very tip of the root and state whether 



root hairs are there present or absent. 



2. State whether the root-hairs are longest near the tip 



or in the direction of the grain. 



3. Make a drawing much enlarged to show the shape of 



one of the roots including the root-tip and the 

 various lengths of root-hairs. Label root-tip, root- 

 hairs. 



C. Microscopical structure of the tip of a root. (Optional.) 



Examine with the aid of the low power of the compound micro- 

 scope a root- tip mounted on a slide in drop of water and covered 

 with a cover glass. Make a sketch very much enlarged to 

 show 



