The pistil is a little bowed upwards, with the stigma seated between the anthers of the short and long stamens, so that this plant was mid-styled. Eight flowers were fertilised with green pollen, and six with yellow pollen, but not one set fruit. This latter fact by no means proves that the plant is heterostyled, as it may belong to the class of self-sterile species. Another plant growing in the Botanic Gardens at Calcutta, as Mr. J. Scott informs me, was long-styled, and it was equally sterile with its own pollen; whilst a long-styled plant of L. reginae, though growing by itself, produced fruit. I examined dried flowers from two plants of L. parviflora, both of which were long-styled, and they differed from L. Indica in having eight long stamens with thick filaments, and a crowd of shorter stamens. Thus the evidence whether L. Indica is heterostyled is curiously conflicting: the unequal number of the short and long stamens, their extreme variability, and especially the fact of their pollen-grains not differing in size, are strongly opposed to this belief; on the other hand, the difference in length of the pistils in two of the plants, their sterility with their own pollen, and the difference in length and structure of the two sets of stamens in the same flower, and in the colour of their pollen, favour the belief. We know that when plants of any kind revert to a former condition, they are apt to be highly variable, and the two halves of the same organ sometimes differ much, as in the case of the above-described anther of the Lagerstroemia; we may therefore suspect that this species was once heterostyled, and that it still retains traces of its former state, together with a tendency to revert more completely to it. It deserves notice, as bearing on the nature of Lagerstroemia, that in Lythrum hyssopifolia, which is a homostyled species, some of the shorter stamens vary in being either present or absent; and that these same stamens are altogether absent in L. thymifolia. In another genus of the Lythraceae, namely Cuphea, three species raised by me from seed certainly were homostyled; nevertheless their stamens consisted of two sets, differing in length and in the colour and thickness of their filaments, but not in the size or colour of their pollen-grains; so that they thus far resembled the stamens of Lagerstroemia. I found that Cuphea purpurea was highly fertile with its own pollen when artificially aided, but sterile when insects were excluded. (4/11. Mr. Spence informs me that in several species of the genus Mollia (Tiliaceae) which he collected in South America, the stamens of the five outer cohorts have purplish filaments and green pollen, whilst the stamens of the five inner cohorts have yellow pollen. He therefore suspected that these species might prove to be heterostyled and trimorphic: but he did not notice the length of the pistils. In the allied Luhea the outer purplish stamens are destitute of anthers. I procured some specimens of Mollia lepidota and speciosa from Kew, but could not make out that their pistils differed in length in different plants; and in all those which I examined the stigma stood close beneath the uppermost anthers. The numerous stamens are graduated in length, and the pollen-grains from the longest and shortest ones did not present any marked difference in diameter. Therefore these species do not appear to be heterostyled.)]
Oxalis (Geraniaceae).
(Figure 4.11. Oxalis speciosa (with the petals removed). Left: Long-styled. Centre: Mid-styled. Right: Short-styled. S, S, S, stigmas. The dotted lines with arrows show which pollen must be carried to the stigmas for legitimate fertilisation.)
In 1863 Mr. Roland Trimen wrote to me from the Cape of Good Hope that he had there found species of Oxalis which presented three forms; and of these he enclosed drawings and dried specimens. Of one species he collected 43 flowers from distinct plants, and they consisted of 10 long-styled, 12 mid-styled, and 21 short-styled. Of another species he collected 13 flowers, consisting of 3 long-styled, 7 mid-styled, and 3 short-styled.