In August 1994，entire purple loosestrife(千屈莱)plants were harvested from three habitats(生长环境)：1) an upland old field in the Cuyahoga Valley National Recreation Area in north-eastern Ohio (n=5)；2) a shallow ditch along Route 261 in Kent, OH (n = 10); and 3) the western shoreline of East Twin Lake, Portage County, OH (n = 6). These sites represent habitats which are never inundated(淹没) with water, are periodically inundated, or have saturated(浸透) soils, respectively. Shoot sections (嫩枝条)of 5, 10, and 15 cm lengths were cut from these plants and positioned in flats(平地) containing a soil mixture of perlite (珍珠岩), vermiculite ( 蛭岩), and peatmoss (苔泥炭) ( 1:1:1). The flats were maintained in the Department of Biological Sciences' greenhouse where they experienced ambient meteorological conditions except for 6 seconds of mist every 3. 5 minutes between 8: 00 and 20: 00 hours daily. Shoot sections and attached leaves were examined at weekly intervals for pigment (色质) and tissue changes as well as for development of lateral shoots. After 26～28 days the sections were rinsed to remove adherent material and dried at room temperature (approximately 22℃ ) for a week. The adventitious roots from each section were removed with needle-nose forceps, dried at 60℃ for 24 hours, and then weighed to determine dry biomass. One lake site 5-cm section was lost during processing.
 The program evaluated in this research was a correspondence training course entitled "Quality Water for Home and Farm" developed for county extension agents( 函授部学员). The program began with a one-day meeting followed by seven monthly written lessons. The program concluded with another one-day meeting. The one lesson-per-month format was selected to allow agents to complete the assignments as part of their regular work schedule.
 The program followed a simple model for identifying water quality problems and potential solutions.
Step 1: Identify the beneficial uses of water (such as for drinking water, livestock water, irrigation, recreation).
Step 2: Test the water to ensure that it is of sufficient quality for the beneficial use.
4. Find and develop a new water supply.
 Steps 1 and 2 on water testing were presented to participants in the initial six-hour meeting. The first correspondence lesson also covered water testing. The six remaining correspondence lessons addressed each of the options for solving water quality problems. Water treatment was divided into three lessons; disinfection, treatment of nuisance waters, and removals of toxins. The final lesson and final meeting covered the development of new water supplies. Each written lesson contained reading material, references, teaching materials, questions, calculations, and exercises.
Agents taking the water quality correspondence training were required to return assignments each month to remain enrolled in the program. Letters of encouragement were sent to delinquents. At the end of the program, extension agents who completed the program received certificates. A list of graduates was distributed to extension administrators, faculty, and staff.
The participants were tested to evaluate the extent of learning. Simple tests were constructed of true/false, multiple choice, and fill-in-the-blank questions to address the important aspects of the program using methods described by Ary et al. (1990). A written pretest was administered at the beginning of the first meeting. A post test of similar but different questions was administered at the end of the closing meeting. The purpose of the pretest was to measure the previous knowledge of the participants. The participants may also learn the subject matter from the pretest, become familiar with the testing approach and therefore be less anxious when taking the post test.