Water and the Plant 79 



ing in the garden if a continuous supply of water does 

 not flow into it through the roots. When insects (such 

 as the squash borer) burrow into stems and cut off and 

 eat out the vessels that carry water upward, the plant 

 soon wilts and may die (page 330). The clubroot disease 

 of cabbage (page 289) often interferes with the work of 

 the roots to such an extent that the infested plant wilts 

 during the day and seldom grows up to be a good plant. 

 The cucumber wilt is caused by a bacterium that enters 

 the vessels and by its growth interferes with the ascent 

 of water, which soon causes the plants to wilt and die. 

 Such injuries as these make evident to us how necessary 

 is the supply of water to all parts of the plant. To re- 

 place that which is lost to the air there must be a cor- 

 responding intake through the roots from the soil. 



Knowing these facts, it is easy to understand why in 

 transplanting seedlings the young plants must not be 

 allowed to become dry ; why they need protection from 

 the sun and air until they get a new root system estab- 

 lished ; why in cultivating and weeding care should 

 be used not to damage the roots of crops ; why cer- 

 tain diseases and insect pests must be combated ; 

 and why it is so important for the soil of the garden to 

 have in it sufficient water for the growing crops. 



Capillary water in the soil. As the water from rain or 

 snow or irrigation sinks through the upper layers of the 

 soil, some of it sticks to the soil particles and is held over 

 and between them as a thin film on their surfaces. This 

 water is called capillary water. A good soil holds large 

 amounts of capillary water in this way, and as the root 

 hairs push in among the granules they come in contact 



