8 STUDIES IN THE VEGETATION OF THE STATE 



ing a quarter inch mesh. In experiments iu the plant-house, 

 the Suils were usually looser than found in nature. It was 

 impossible during the length of time used for experimenta- 

 tion to measure the degree of hardness, yet this must de- 

 termine to a greater or less degree the extent and course of 

 the rootlets of the plant. Such being the case, the hard 

 soil may limit the extent of a plant's roots and become an 

 direct factor in times of drought because it may thus hasten 

 the death of the plant by limiting its ability to secure water. 

 In order to roughly estimate the condition of the soil, it has 

 been indicated in the summary of results as loose, medium, 

 and hard in density. In case of plants grown for experi- 

 mentation, the soil being loose at first, most of them had an 

 opportunity to become well rooted before it became hard, 

 and as a result the hardness of the soil is not considered as 

 a factor affecting the death of the plants to an appreciable 

 degree. 



2. Water in Soils. Since the amount of water a soil may 

 hold is measured by the space between the particles of soil, 

 the water capacity was determined for each of the six soils 

 used by a simple experiment which is described under Phys- 

 ical Water. The amount of physical water present in the 

 soil was determined by taking samples from the pots with 

 a tubular soil sampler. These were weighed at once to pre- 

 vent error from evaporation, and subjected to a heat of 

 212° P. for about 24 hours; then the per cent was determined 

 from the loss in weight. The evaporation of slight amounts 

 of volatile organic water was not taken into consideration in 

 the results. The amount of water in the soil not available 

 for the plant was found in the same way as the physical 

 water, except that it was determined when the plant was 

 near the death point, as evinced by the condition of the 

 organs of the plant. The exact time when a plant can no 

 longer get water from the soil is difiQcult to decide, but the 

 rule followed in most cases was to take the soil sample at 

 the time the youngest leaves of the plant wilted strongly, 

 though in many cases the plant was actually dead at the time of 

 the estimate. This will account for most of the irregularities 



