WATER-CONTENT 



35 



research, the chresard must of course be ascertained for each formation with 

 respect to its pecuHar plants and soil. The influence of the ecad in more or 

 less determining the echard is also shown by Hedgcock, who found that 

 floating plants wilt at- 25 per cent, amphibious ones at 15-20 per cent, 

 mesophytes at 6-12 per cent, and mesophytic xerophytes at 3-6 per cent. 

 The echard is also somewhat higher for shade plants than for heliophytes. 







Records and Results 



55. The field record. It is superfluous to point out that a definite form 

 for field records saves much time and prevents many mistakes. The exact 

 form may be left to personal taste, but there are certain features which are 

 essential. Many of these are evident, while others may seem unnecessary; 

 all, however, have been proved by experience to have some value in saving 

 time or in preventing confusion. The two fundamental maxims of field work 

 are that nothing is too trivial to be of importance, and that no detail should 

 be entrusted to the memory. The field record should contain in unmis- 

 takable terms all that the field has yielded. These statements apply with 

 especial force to water-content, in many senses the most important of 

 physical factors. The precise character of the record depends upon the way 

 in which the readings are made, whether scattered or in series. As the 

 day-station series is of the greatest importance, the record is adapted for it 

 e&pecially, but it will also serve for all readings. The record is chronolog- 

 ical, since this is the only convenient method for the field. A proper form 

 for a field record of water-content is the following: 



A general designation of the soil-composition is a material aid, especially 

 where there is a difference in the core. For example, in a mountain forest 

 or meadow, the upper layer will usually be mold, the lower sand or gravel. 

 A careful estimate of the relation between the two throws much light upon 

 the chresard. Under "sample" the number taken to reach the desired depth, 

 if more than one, is indicated by placing the number before the depth, thus 

 2:10. When two or more full cores are included in the same sample for a 



