62 BULLETIN 545, U. S. DEPARTMENT OF AGRICULTURE. 
held together by the intertwining of the roots was wrapped in burlap 
for purposes of transfer and immediately placed upon suitably cut 
wire screen (see Plate I), which, when fitted and fastened together 
around the soil body in the form of a basket, was placed in the hole 
created by the digging of the plant. In this manner the plant was 
not subjected to too rapid drying and its normal functions were 
unimpaired. After the plant had fully recovered from any slight 
disturbance due to digging, it was elevated slightly in order to 
increase the rapidity of the drying process. The wire-basket method 
made the plant portable, a very desirable feature in field work since 
the plant could easily be removed from the field during showers and 
when in a wilted condition prior to soil sampling and piaced under 
shelter — in this case in a carefully-placed 14-ounce canvas 'tent — and 
thus protected from direct effects of wind and sun when the specimen 
might recover its turgor if not wilted excessively. 
The other method of ascertaining the water requirements was to 
dig away the soil on all sides of the plant, leaving in place the central 
core of soil supporting the roots, the size of which would depend upon 
the spreading habit of the root system (see Plate I, fig. 2). This 
method was used especially for certain species with deeply pene- 
trating taproots, such as wild celery (Ligusticum oreganum) and wild 
buckwheat (Polygonum pliytolaccaefolium). These, it was found, 
would not respond normally to the wire-basket method of treatment. 
The drying process brought about in this way, owing to the fact that 
the water supply was not wholly cut off from below, was slightly more 
gradual than in the case of the wire-basket method, but the results 
of the tests for species which did not have a distinct taproot, such as 
grasses, proved to be virtually the same as those secured for the same 
species by the wire-basket method. When the plant reached a con- 
dition of pronounced wilting and turgor could not be recovered, two 
representative soil samples were taken, weighed immediately to avoid 
possible discrepancy due to evaporation, placed in a soil-drying oven 
and subjected to a temperature not exceeding 212° F. for several 
hours until they were dry, then reweighed. The difference between 
the dry weight of the samples and the weight when taken at the time 
the plant was in a wilted condition represents the amount of moisture 
remaining in the soil at a time when the root hairs were unable, under 
the conditions, to absorb moisture rapidly enough to maintain the 
form of the plant and finally to recover its turgidity. The depth and 
location at which soil samples were taken were regulated by the 
depth of penetration and position of the roots. This operation was 
followed by protecting the specimen from the direct effect of sun and 
wind by placing a small tent shelter over it. In all cases the soil 
moisture figures given are based upon specimens which failed to 
recover their turgor, unless otherwise stated. All moisture require- 
