6 LOUISE DOSDALL 



sary to produce it, or in respect to the kind of plants or plant 

 parts affected, been so thoroughly worked out as to permit a 

 close application to the problem in hand. It is obvious that 

 to fit the case, marsh or bog conditions must have produced 

 pseudoxerophytic adaptations in the great mass of the tree 

 growth, but not in ferns and spenophyllous plants. The effects 

 must apparently also be extended to all plants brought into the 

 depositing basins by drainage, whether these were true swamp 

 plants or not, unless a closer study of the coal flora shall show 

 that the xerophytic aspect was not assumed by all species of 

 the trees involved. It is clear that a more critical study of the 

 problem on all sides is necessary before a final conclusion can be 

 reached." 



Dachnowski (1912: 278) questions this theory on the ground 

 that the plants encountered adversities of soil-water content 

 rather than of climate. 



II. METHODS 



The general plan followed was to make a quantitative com- 

 parison of the water used by Equisetum and that used by certain 

 other plants of well known habits. The latter include Bryo- 

 phyllum calycinum, a xerophyte, Helianthas annuus and Phaseo- 

 lus vulgaris, mesophytes, and Ranunculus sceleratus, an am- 

 phibious hydrophyte. Under the term "water requirements" 

 the water used in various ways by the plant is included, the 

 purpose being to determine whether in its physiological 

 processes Equisetum uses more or less water than the other 

 plants. 



(1) SOURCE OF PLANTS 



In the spring of 1916 attempts were made to transplant the 

 fertile stems of Equisetum arvense into glazed pots in order to 

 compare their rates of transpiration. No matter how carefully 

 the plants were taken up or how little the soil was disturbed, 

 they wilted almost as soon as they were put in the greenhouse. 

 This may be accounted for by the fact that the rootstocks of 

 this species grow very deep into the ground and it was always 



