136 PLANT LIFE ON THE FARM. 



plant may not be visibly or materially injured. The 

 effects will be first and most especially obvious at the 

 point of injury, and at the growing points where the life- 

 functions happen to be going on most vigorously at the 

 time. Thus, if the young shoots and young leaves are in 

 full activity at the time when root-mischief occurs, they 

 will the soonest show the effect of cutting off supplies 

 they will wither and droop. If the process is slow and 

 gradual, the leaves will become emptied of their contents. 

 their chlorophyll will change colour, the plant will assume 

 a sickly yellow look very characteristic to the practised eye. 

 The older portions of the plant, with their reserve stores 

 of water and food, may not immediately suffer ; and it is 

 from them that the materials requisite for any effort at re- 

 pair and reorganisation must, if it be possible, be made. 

 Thus a plant may grow for some time after injury and then 

 suddenly flag because its reserve supplies are at length 

 exhausted. It follows from this that death from starvation 

 as a consequence of root-mischief is not generally a sudden, 

 but more often a gradual process, the length of time of 

 course varying according to the nature of the mischief, and 

 specially according to the nature and condition of the 

 plant. 



Death beginning at the Leaf. This may be appre- 

 ciated from what has been before said as to the functions 

 of the leaf. The leaf is an organ of nutrition, of respiration, 

 and transpiration; if its functions are sufficiently inter- 

 fered with, death will result, either from inanition or 

 from suffocation or from both combined. The power of 

 resistance that a leaf has may be inferred from its 

 structure. A thick fleshy leaf with layer after layer of 



