The methods for the quantitative monitoring studies are described 

 by Shelly (1989) . 



RESULTS: The results of the population size surveys are 

 presented in Table 3. Even though these figures are to be 

 strictly regarded as estimates, they indicate that most 

 populations remained fairly stable in size from 1987 to 1989. 

 Obvious changes in abundance were noted in four populations (012, 

 023, 025, 056). Also included in Table 3 are 1989 estimates of 

 the percentage of each pond that is occupied by H. aquatilis . 

 These estimates correlate well with the population size estimates 

 (smaller populations generally occupy the smallest percentage of 

 suitable habitat) . These percentage figures may provide an 

 additional means of tracking the abundance of H. aquatilis 

 through time, and can often be obtained without adversely 

 affecting the populations. 



The results from the line-transect studies for two years are 

 presented in Table 4, pp. 7-8. The four ponds for which water 

 depth measurements were taken in both 1988 and 1989 were all 

 deeper during the second year, which was more normal with respect 

 to precipitation and run-off. Pond numbers 020 and 027 were 

 significantly fuller during 1989. 



The percent cover of Howell ia aquatilis was higher in 1989 than 

 in 1988 in four of the five ponds studied. Significant increases 

 were noted in two of these (008 and 020) , in which the percent 

 cover along the line transects increased from 8.21 to 27.40, and 

 26.29 to 59.21, respectively. These observations are in keeping 

 with previously observed fluctuations in population size (Shelly 

 and Moseley 1988) . 



DISCUSSION: The possible reasons for fluctuating sizes in 

 Howellia populations are addressed by Lesica (1990), and include 

 the date of pond drying each year; it is hypothesized that 

 optimal population development occurs in sites that dry down in 

 wet years and do not dry too early in dry years. If drying 

 occurs too early in the season, seed production may be reduced; 

 if drying is much delayed during a wet year, the normal fall 

 germination of seeds would be much reduced or eliminated. Either 

 of these events could result in much lower numbers of individuals 

 the following year. The observed decline in population 012 may 

 have been a result of a suboptimal drying regime in 1988 (a 

 drought year) . If that pond had dried too early owing to the 

 drought conditions, seed production could have been so reduced 

 that the low number of observed individuals in 1989 may have 

 resulted. Conversely, the observed increases in estimated 

 abundance in populations 023 and 025, and the measured increases 

 in populations 008 and 020, may reflect optimal drying regimes 

 (and resultant germination success) at those sites during 1988; 

 the appearance of H. aquatilis in pond 056 in 1989 may also 

 reflect favorable conditions in 1988. These results suggest that 

 every pond is different with respect to drying regime and 



