152 THE GROWTH OF BOOTS AND STEMS. 



When the root has grown about 2 inches long, dry its 

 surface carefully, stroking it with torn bits of blotting-paper, 

 and with a fine brush mark it at intervals of J inch, starting 

 at the tip, with dots or transverse lines of Indian ink. 



The stem of a French or Runner Bean seedling should be 

 marked in the same way, starting at the point where the 

 first pair of foliage-leaves stand on the stem and working 

 downwards ; seedlings of Sunflower or Mustard may be 

 used, the hypocotyl being marked starting from the coty- 

 ledons. 



* 183. Where does Growth in Length occur? Pin a 



seedling with marked root to the cork of a glass jar, exactly 

 as in Fig. 15. Examine from time to time and note the 

 positions of the marks; after a few days, the marks just 

 behind the tip of the root will be widely separated, while 

 those farther back have changed little, or not at all, in 

 position. What conclusion can you draw from the results of 

 experiments like this ? To what region of the root is growth 

 in length almost entirely restricted? 



A neat method of arranging this experiment is to put the 

 seedling into a thistle-funnel and let the root grow down the 

 tube ; the latter is set in a jar of water, while the seed is 

 covered with some wet blotting-paper or cotton-wool. This 

 plan, allowing the roots to grow very long, gives striking 

 proof of the fact that growth in length chiefly occurs just 

 behind the root- tip. An ordinary glass funnel may be used 

 instead of a thistle-funnel. 



Daily observations and measurements of the hypocotyl 

 of a French Bean seedling, or the young shoot of a Runner 

 seedling, will show that in the stem, as in the root, growth 

 in length is much more vigorous just behind the tip than 

 farther back. 



184. How the Young Boot enters the Soil. You 



have seen that the root end of the axis is the first part of the 

 young plant to emerge from the seed, and that on emerging 

 it grows downwards, in whatever position the seed has been 

 placed. Have you tried the effect of moving the seed at 

 this stage, and then turning it over each time the root has 



