34 LOUISE DOSDALL 



through mesophytes, to xerophytes" and the view of Clements 

 (1905:31) that "a plant of xerophytic tendency is naturally 

 able to remove more water from the same soil than one of 

 mesophytic or hydrophytic character." Briggs and Shantz 

 (1912:75) found the wilting coefficient of a great number of 

 plants with which they worked to vary but little, or from 92 

 for Japan rice to 106 for a variety of corn, with 100 as the 

 standard. From their results of simultaneous wilting of plants 

 grown together in the same pots, the writers conclude that one 

 plant is not able to draw more moisture from the soil than 

 another. The results of the present investigation indicate that 

 certain mesophytes are able to take more moisture from the soil 

 than the hydrophytic species of Equisetum can. 



2. WATER LOSS BY THE PLANT 



(1) Comparative transpiration 



A comparison of the series in Table 5 shows that in the amount 

 of water lost by transpiration Equisetum fluviatile exceeds both 

 the mesophytes and the xerophytes. Ranunculus sceleratus, 

 which is a typical hydrophyte, loses only eight to nine tenths 

 the amount of water that Equisetum fluviatile does. The meso- 

 phytes Helianthus annuus and Phaseolus vulgaris lose from two 

 to six-tenths as much, while the xerophyte, Bryophllum caly- 

 cinum, loses only one tenth as much. In other words Equisetum 

 fluviatile transpires from two to five times as much water from 

 its surface as do two typical mesophytes, and ten times as much 

 as a typical land xerophyte. Ranunculus is an exceedingly 

 plastic species which accounts for its ranking below Equisetum, 

 for during the experiment the roots of the former were not in 

 water. Helianthus is an exceedingly wasteful plant as far as 

 water loss is concerned which explains the transpiration being 

 higher than in the case of Phaseolus. The conclusion to be 

 drawn from this evidence is that Equisetum fluviatile is un- 

 questionably a hydrophyte. 



These results agree very closely with those of Sampson and 

 Allen (1909:55) who found that Scirpus lacustris also a "bog 

 xerophyte" loses twice as much water as Helianthus annuus. 



