same form, and these grains differed in diameter in the ratio of 100 to 90. The mean diameter of these two lots of twenty grains was to that of twelve grains from another short-styled flower as 100 to 75: here, then, the grains from the short-styled form were considerably smaller than those from the long-styled, which is the reverse of what occurred in the former instance, and of what is the general rule with heterostyled plants. The whole case is perplexing in the highest degree, and will not be understood until experiments are tried on living plants. The greater length, and more papillose condition of the stigma in the short-styled than in the long-styled flowers, looks as if the plant was heterostyled; for we know that with some species--for instance, Leucosmia and certain Rubiaceae--the stigma is longer and more papillose in the short-styled form, though the reverse of this holds good in Gilia, a member of the same family with Phlox. The similar position of the anthers in the two forms is somewhat opposed to the present species being heterostyled; as is the great difference in the length of the pistil in several short-styled flowers. But the extraordinary variability in diameter of the pollen-grains, and the fact that in one set of flowers the grains from the long-styled flowers were larger than those from the short-styled, is strongly opposed to the belief that Phlox subulata is heterostyled. Possibly this species was once heterostyled, but is now becoming sub-dioecious; the short-styled plants having been rendered more feminine in nature. This would account for their ovaries usually containing more ovules, and for the variable condition of their pollen-grains. Whether the long- styled plants are now changing their nature, as would appear to be the case from the variability of their pollen-grains, and are becoming more masculine, I will not pretend to conjecture; they might remain as hermaphrodites, for the coexistence of hermaphrodite and female plants of the same species is by no means a rare event. Erythroxylum [sp.?] (Erythroxylidae). (FIGURE 3.8. Erythroxylon [sp.?] Left: Long-styled form. Right: Short-styled form. From a sketch by Fritz Muller, magnified five times.)