Plants in Relation to Man 463 



The importance of root hairs is strikingly shown by a plant 

 which has just been transplanted. For several days such a plant 

 wilts, regardless of the nature of the soil and the care with which 

 soil is packed about the roots. What does this indicate as to the 

 condition of the root hairs and their importance to the plant ? 

 Can plants get the water and food materials they need from the 

 soil without root hairs ? Can they get enough of these materials 

 if the root hairs are injured to any considerable extent? 



This suggests the proper time for transplanting. If the plants 

 are in full leaf and transpiring their usual quantity of water, 

 can they be transplanted advantageously? Would it appear 

 to be better to transplant them when they are not in leaf, as 

 in early spring or late autumn ? What facts have you observed 

 which support your answer to this question? If the plants to 

 be transplanted are in leaf, would pruning or trimming them 

 be advisable? Why? 



223. Transpiration. That plants absorb and release 

 through transpiration and evaporation large quantities of 

 water as vapor may be illustrated experimentally in many 

 ways. The several methods described in the following experi- 

 ments should be considered primarily as suggestive ; and you 

 should devise ways and means of your own to demonstrate 

 it. You may find by observation many signs of the process 

 in plants, especially on hot days. 



Exercise. Take a potted p'ant which requires a considerable 

 amount of moisture (certain lilies, such as the Chinese lily, will do) ; 

 give it a full supply, and then wrap the pot carefully in a piece of 

 sheet rubber (or moisture-proof oiled paper), closing it well around 

 the plant stalk just above the soil or water surface. Weigh the whole 

 accurately. Weigh again at intervals of four to six hours for two or 

 three days. Be careful to prevent evaporation of the water except 

 through the plant. The following data will be instructive. 



Weight of pot wrapped, Weight after 30 hours 



Weight after 6 hours Weight after 36 hours 



Weight after 12 hours Weight after 48 hours 



Weight after 24 hours 



