46 THE VEGETATIVE ORGANS 



chamber in which to grow the seedling. Push a large pin 

 through the cork and fix the Bean seed firmly to the point ; 

 then replace the cork in such a way that the marked 

 radicle hangs downwards within the bottle so as to avoid 

 touching the sides. Make a sketch of the radicle at the 

 commencement of the experiment, showing the exact 

 number of lines and their distance apart, and at the end 

 of two or three days make another sketch and note what 

 has happened (Fig. 21, 2). Has the root grown ? Count the 

 lines and compare them with the original sketch. What 

 is their position now ? Which lines are most widely 

 separated ? What changes have occurred in some of the 

 lines ? Has elongation occurred at the extreme tip, or is 

 the position of the first line still unchanged ? We observe 

 that the extreme tip (the end of the root-cap) has not 

 grown, but that elongation has been most active in the 

 region immediately behind this and included within the 

 next two or three lines, which, as the root has elongated, 

 have been drawn out and now appear as a number of 

 dots. 



Region of curvature. Mark the radicle of another Bean 

 seedling and place it in a moist chamber as before, but 

 fix it with the radicle horizontal. Allow it to grow, and 

 note where curvature takes place. Observe that the regions 

 of curvature and elongation coincide and are included 

 within the last quarter of an inch, but the sensory region 

 (p. 40) is confined to the last sixteenth of an inch of the 

 root-tip. 



If the experiments have been carried out successfully, 

 the seedlings may be used for observing the manner in 

 which the branch roots emerge. Replace the seedlings and 

 allow them to grow a few days longer. Note that they 

 come out in four, sometimes five, vertical rows ; that they 

 are not in any way related to leaves, and grow out obliquely 

 from the radicle. In cases where the radicle has been 



