Morphological observations were made on fruits, seeds, stems, leaves, and flowers of 13 species of Yucca at various locations in California, Arizona, and eastward. The dates of flowering, fruit production, and fruit fall (or fruit persistence) were recorded. Seed samples for 12 of the 13 species were weighed, and fell into two different weight classes: light and heavy. It was observed that the species producing light seeds had a suite of five other correlated morphological characteristics. Conversely, most of the heavy-seeded yucca species had five different or contrasting features. Neither the seed weight classes nor their systematic correlation with the other five traits were covered in the Yucca literature consulted. Seeds of 14 additional Yucca species and one Yucca subspecies, taxa that were unavailable during the field studies, were commercially available from seed suppliers. It was possible to determine from the literature which of these 14 species possessed dehiscent pods, one of the attributes correlating with light seeds; and which ones produced indehiscent pods—the contrasting feature regularly associating with heavy seeds. The weights of the purchased seeds were consistent with the predictions that: (1) seeds from plants known to possess dehiscent pods would be light, and (2) the seeds from plants having indehiscent fruits would be relatively heavy. The few exceptions to other correlated features are listed and analyzed. It is proposed that the five features correlating with light seeds aid in transport of the seeds by wind. It is further hypothesized that the five contrasting attributes, which are usually present in heavy-seeded yuccas, foster seed dispersal by animals. These two hypotheses find support in the present data. Several additional morphological traits were analyzed and appear to be unrelated to seed dispersal or to phylogeny, posing a problem for neo-Darwinian macroevolution. The yucca correlations support a nonevolutionary origins model for Yucca species. Based on these data, further predictions are made, including the prediction that the correlations of seed weight with other features will also exist in the species and subspecies of Yucca not yet analyzed. Other possible avenues for future yucca research are enumerated.