LABOR Aran r studies of the root 35 



layer of the leaf and stem in being more or less impermeable by water. 

 Does the central cylinder of the taproot connect directly witli those 

 of the lateral roots and rootlets? 



Experiment 7. — What part of the root conveys liquids up to the 

 leaves of the shoot? Determine this by cutting off the lower half of 

 the main root and the ends of some other roots, and placing the still 

 leafy plant with these cut surfaces in water colored with eosin. After 

 a time cut off the cortex on one side of the root, at different levels, to 

 find whether the eosin water has been taken up ; and, if so, what path 

 it has followed. Save a thin cross section of the taproot for drawing. 

 Draw : (1) The general habit of the root system, to show the points 

 already mentioned. Show the rings or wrinkles due to longitudinal 

 contraction. (2) A piece of the branching fibrous root (as seen with 

 the dissecting microscope, and therefore much magnified), showing the 

 points noted above. (3) Longitudinal section of taproot (short piece), 

 showing the wood, cortex, and coating, and the connections with 

 branches (x3-4). (4) Cross section of the taproot (x4-5). 



Exercise XV. Roots for Climbing 



Make a drawing of the given stem with its climbing roots, to show 

 the mode of occurrence of the roots, whether in rows or not, and 

 whether at or near the nodes of the stem or not. With the lens, 

 examine the roots for root hairs. Is there any sign that they play a 

 part in the adhesion of the roots to supporting surfaces? 



Exercise XVI. Roots for Storage 



Compare the internal structure of the given root with that of Shep- 

 herd's Purse. Are all the regions which were observed in that root 

 found in this one? In what region or regions of the storage root is 

 thickening most pronounced? In what part or parts is nourishment 

 stored? How can you test this? What part does this root play in the 

 life history of the plant? Will the root grow — i.e. give rise to shoots 

 — when planted in a pot of earth? (Try it.) 



Is any part of the stem of the plant present and closely incorporated 

 with the root? Distinguish root and stem carefully in such a case. 



Draw whatever diagrams are necessary to illustrate your notes. 



Supplementary Subjects 



1. The roots of epiphytic Orchids. Xote their origin and structure, and 

 behavior toward water. What is the habitat of these plants? 



2. Roots of the Dodder. 



3. Contraction of the roots of plants. 



4. Direction of growth of roots under influence of moisture. 



5. The rate of growth of the roots of seedlings. 



6. Root pressure shown by guttation. 



