GROWTH IN LENGTH. 37 



commencing as close to the tip of the root as 

 possible and continuing them backward for 

 about one inch. These lines should not be 

 more than th. inch apart, and in marking 

 them great care must be taken not to injure 

 the root. 



3. Pin the seedling, with the root hang- 

 ing vertically, on the inside of a box, the 

 atmosphere in which is kept moist, as in the 

 experiment with germinating maize. The best 

 method of fastening the seedlings is to pass 

 an ordinary pin through the ' two cotyledons, 

 taking care not to injure the young stem or 

 root. Examine after twenty-four hours, com- 

 paring the marks on the root with those on 

 the card. 



4. It should be found that the first one 

 or two divisions, near the tip, have not altered 

 in length ; that the next ones have grown a 

 great deal ; while those still further back have 

 remained stationary like those at the tip. 



5. Thus we see that in a root the greatest 

 amount of growth is not at the apex, but some 

 little way behind it, so that the root- tip pro- 

 tected by its root-cap is, as it were, driven 

 down through the soil by the rapid growth 

 of the portion just behind it. 



