VI. ABSORPTION OF WATER BY PLANTS 



A. External Anatomy of the Root: 



1. Examine roots of seedlings (mustard, flax, oats, 

 etc.), grown in a moist chamber (e.g., flower-pot, 

 or saucer of same) in the dark, and kept covered 

 with a glass plate so as to expose them to the air 

 as little as possible. Note the delicate white hairs 

 on them. Describe their distribution and relative 

 size. These hairs are root-hairs. 



2. Hold the root up to the light and note the more 

 transparent tissue on the end (root-cap), covering 

 the root-tip proper. How is the latter distin- 

 guished? Is " root- tip" synonymous with "end of 

 the root?" Explain. 



3. Make a drawing of the seedling, at least twice 

 natural size, showing these features. (The labeling 

 of the root-cap and root-tip may be deferred until 

 observation B, 3, below, has been made. ) 



B. Microscopic Characters of the Root: 



1. With the scalpel carefully remove the terminal 

 5 to 6 mm. of a root, with the root-hairs, and mount 

 it in water. Locate the oldest and youngest root- 

 hairs. How are they distinguished? Do they 

 branch? What relation do the hairs bear to the epi- 

 dermis ? Are they divided by cross-walls ? Do they 

 contain nuclei? What is a root-hair, structurally? 



2. Make a drawing (high power) of three or four hairs, 

 showing their structure and relation to the epider- 

 mis. The hairs should be drawn at least 50 to 75 

 mm. long. 



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