74 SOIL AND ITS RELATION TO ROOTS 



Pt'ohle^n 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. 



