SUMMARY In the plant sciences, surveys are frequently conducted in the following way. Small and clearly demarcated sample units of fixed and constant size and shape are randomly located within a tract. Each species of interest is recorded as being either present or absent on each sample unit. Such sample units are called 'quadrats'. A quadrat is said to be 'stocked' with a particular species when the species is present, and the proportion of quadrats stocked is called the 'frequency' in ecology, or the 'stocking' in forestry. Such surveys are here called 'stocked- quadrat surveys'. Frequency has long been recognized as a fundamental and important attribute of the spatial dispersion of plants. Brown (1954) gave a brief account of the historical development of the concept in ecology. Moreover, stocked-quadrat surveys are relatively easy to conduct compared to surveys in which the actual number of individual plants in each quadrat is enumerated. Consequently, stocked-quadrat surveys are sometimes employed even when the primary objective is the estimation of 'abundance' or 'density', i.e. the average number of individuals per unit area. In any event, frequency data can always be examined for infor- .~~~~~~~~~~~~~~21 where X (> 0) is density per unit area, say average number per hectare, and q (> 0) is quadrat size measured in the same units of area. In stocked-quadrat sampling the only record made for the ith quadrat is whether it is stocked (Xi - 1) or not (Xi = 0). Thus, the random variable