10 LOUISE DOSDALL 



collapse of the tissue at the point of sealing. A damping-off 

 fungus also produces a sudden wilting, but in this case the stem 

 always shows decay at the surface of the soil. In wilting due 

 to lack of water in the soil, the top of the plant collapses first 

 and the stem is not injured at the surface of the soil or at the 

 point of sealing. 



Ranunculus sceleratus on the other hand has no definite wilting 

 point. The time of the yellowing of the first leaves of the 

 rosette varies from four to eight days. By the time theyounger 

 parts wilt the older parts are completely dead. As these parts 

 continue to draw water from the soil and evaporate it from 

 their leaves (Briggs and Shantz 1912: 47), the coefficients are 

 too low. 



The relative time of wilting was compared with that of meso- 

 phytes such as Helianthus annuus and Phaseolus vulgaris by 

 growing them in the same pots (fig. 1) and allowing them to 

 wilt. In some cases the Equisetum and the beans and sun- 

 flowers were started in the same pots, in others, plants from ten 

 to twelve days old were transplanted into the same pots, care 

 being taken to injure the roots as little as possible. Two weeks 

 were allowed for the plants to establish themselves and develop 

 good root systems before sealing. 



(3) TRANSPIRATION METHODS 



Water loss by the plant was determined by weighing potted 

 plants as this is the most convenient and reliable of the several 

 methods for measuring transpiration. The plants were either 

 sealed in glazed pots or in Ganong aluminum shells. The wax 

 used as a seal was made of twenty parts of vaseline to eight 

 parts of paraffin, the formula recommended by Briggs and 

 Shantz (1912: 13). In cases where the wax was to be put directly 

 on the soil, a piece of paper was cut to fit neatly over the top of 

 the pot, dipped into the melted wax, and fitted in place. The 

 edges were sealed by pouring more wax over the surface and 

 slightly tipping the pot so that it would run up the sides. The 

 object of the paper was to prevent the wax from creeping into 



