74 SOIL AND ITS RELATION TO ROOTS 



Problem 54: To study the structure and purpose of root 

 hairs. 



Materials. — Radish or mustard seeds, blotting paper, Syracuse 

 watch glasses, thin glass plates, glass slide, cover slip, microscope. 

 Diagrams pages 74, 75, Civic Biology. 



Method. — Grow radish or mustard seeds on blue blotting paper 

 in Syracuse watch glasses, covering each watch glass with a thin 

 glass plate. 



Observations. — Describe the structures you see growing from 

 the roots. These are called root hairs. Where are they the 

 longest? Where the most abundant? 



Place a radish or mustard seedling on a glass slide. Mount 

 in a drop of water and cover with a cover slip. Examine with 

 the low power of a microscope. What can you say of the thick- 

 ness of their walls? Of how many cells does a root hair seem to 

 consist ? 



If the root were covered with these thin-walled, delicate struc- 

 tures, what effect would they have upon the absorbing surface of 

 the root? 



Conclusion. — 1. Tell what you believe to be the purpose 

 (function) of root hairs. Give good reasons. 



2. Why should the wall of a root hair be thin? 



Drawing. — A seedling showing position of root hairs. 



Problem, 55: To discover how fluids travel through roots 

 and stems. 



Materials. — Carrot or parsnip, iodine, red ink, scalpel, micro- 

 scope. 



Method. — Cut a cross section through a fleshy root (carrot or 

 parsnip) and dip in iodine. Also place sprouting parsnips in red 

 ink for two or three days, then cut cross and longitudinal sections. 



Observations. — In a stained cross section note the cortex 

 (outer part) less deeply stained than the wood (the inner part). 



To the Teacher. — Excellent demonstration material may be obtained by 

 placing celery stems in red ink. Asparagus also shows well. Several different types 

 of stems might be shown to bring out differences in dicotyledonous and monocoty- 

 ledonous stem structure. Our next experiment will show us how the fluid gets from 

 the outside to the inside of the root. 



