WATER REQUIREMENT AND ADAPTATION IN EQUISETUM 37 



' jars and the following morning large drops of water were found 

 at the nodes between the points of the leaf scales and much 

 smaller ones in the grooves of the internodes at positions 

 corresponding to those of the stomata. 



This furnishes additional evidence that Equisetum is not a 

 xerophyte and particularly a "bog xerophyte" whose roots are 

 supposed to have low absorption powers. 



(3) TRANSPIRATION AND PHOTOSYNTHESIS 



Relative transpiration and photosynthetic efficiency of Equi- 

 setum fluviatile, Helianthus annuus and Phaseolus vulgaris. 



This experiment was done in cooperation with Miss Frances 

 Long who determined the photosynthate. 



The plants for this experiment were grown in soil kept 

 saturated with water. The morning of the experiment the pots 

 were placed in Ganong aluminum shells filled with water. Evapo- 

 ration from the soil was avoided by covering it with a layer of 

 waxed paper held in place by the aluminum ring. The space 

 between the plant and paper was sealed with the Shantz mixture 

 of paraffin and vaseline. 



For the photosynthate readings similar plants were used for 

 the morning and noon readings, since those used for transpiration 

 could not be destroyed until evening. 



Leaf prints were made of the leaves as soon as cut and the 

 areas found by a planimeter. The leaves were killed in chloro- 

 form and dried in a steam oven at 90°. The glucose determi- 

 nation was made by the modified Munson Walker method used 

 in Miss Long's photosynthate experiments. 



The experiment was carried on May 4, 1917. The tempera- 

 ture and humidity conditions were as shown in table 6. 



A glance at table 6 shows that Equisetum transpires 1.5 as 

 much as Helianthus and 2.3 times as rapidly as Phaseolus. 

 Helianthus loses 1.5 times the amount of water lost by Phaseolus. 

 Helianthus is regarded as a very wasteful plant so far as water 

 efficiency is concerned. 



Helianthus shows 1.8 the ability to make carbohydrates shown 

 by Equisetum, while Phaseolus is three times as efficient as 



