LABOllATOUV tiTC'DIK^^ OF TUB JlOO'r 35 



layer of the leaf ami .stein in lieu-t^' inure nr less imjieriiiealile by water. 

 Does the central cylinder oi' tlie tapi'out connect directly witli lho.se 

 of the lateral roots and rootlets? 



Experiment 7. — Wliat part of tlie root conveys liijuids up to tl;e 

 leaves of the .shoot? Deterniine this \^y cutting off tlie lower half of 

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

 leafy plant with tliese cut siii'faces in water colored witli eosiii. After 

 a. (iiaj cut off the cortex on one side of the root, at different levels, (0 

 lind whether the cosin water has heeii taken up ; and, if so, what jiatl-. 

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

 Draw : (1) The general liahit of the root system, to show the i)oiiit3 

 already mentioned. Show the rings or wrinkles due to longitudinal 

 contraction. (2) A piece (if the liranching fibrous root (as seen with 

 the dissecting microscope, and therefore niitch magnitieil), showing the 

 points noted aliove. (:!) Longitudinal section of taproot (sliort piiece), 

 sliowiug the wood, cortex, and coating, ami the connecfions with 

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



Exercise XV. liOOTs kor C'LniBixG 



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, ami 

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

 examine the roots lor root hairs, is there any sign that they play a 

 part in the adhesion of the routs to supporting surfaces? 



ExERC'SE XVI. Roots foi; Stor.^ge 



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

 lierd's Purse. Are all tlie regions which were observed in that root 

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

 thickening most pronci need? In what part or parts is noui-ishment 

 stored? How can you l.est this? \Vliat part does this root play in tlie 

 life history of the pilantV \Vill the rout grow — i.e. give rise to shoots 

 — wdien planted in a pot of eartli? (Try it.) 



Is any part of the stem of the plant pi-esent and closely incorporated 

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

 ■ Draw whatevei' diagrams are necessary to illustrate your notes. 



Supplementary Subjects 



1. The roots of epiphytic Orchids. Nole llieir oriuiii anil strncfnre, and 

 behavior toward \\'ater. What is the Iialiitat ot tlicso phmts? 



•>. Roots of the Di.dder. 



?.. Contraction of tlie roots of jilaiits. 



4. Direction of ttrowtli of roots under iiilliieiice of moisture. 



."J. The rate of growth of the roots of seedlings. 



6. Root pressure shown by guttatiou. 



