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Show 168 HETEROSTYLED TRil\IORPHIC PLANTS. CHAP. IV. sterile with its own pollen; whilst a long-styled plant of L. reginre, 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. VVe 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 smnetimes differ rnuch, as in the case of the above-described anther of the Lagerstrcemia ; 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 LaO'erstrmmia th . 0 ' at rn 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 Lythracere, namely Cuphea, three sp~cies 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 Lagerstrcemia. I found that Cul!he~ purP_urea was highly fertile with its own pollen when artrficrally aided, but sterile when insects were excluded.* * Mr. Spence informs me that in s~veral. ~pecies of the genus Molha (Tll1acere) whieh 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 trimor-phic: but he did not notice the h:ngth of the pistils. In the allied Luhea the outer purplish stamens are destitute of anthers. I proeured some specimens of Mallia lepidota and speciusa from Kew, but could not make out that their pistils differed in length in different pbnts; and in all those which I examined the stigma stood close beneath the CHAP. IV. OXALIS. 169 OxALIS (GERANIACElE). 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-~tyled. Of another species he collected 13 flowers, consisting of 3 long-styled, 7 mid-styled, and 3 shortstyled. In 1866 Prof. I-Iildebrand proved* by an examination of the specimens in several herbaria that 20 species are certainly heterosty led and trimorphic, and 51 others almost certainly so. He also made some interesting observations on living plants belonging to one form alone; for at that time he did not possess the three forms of any living species. During the years 1864 to 1868 I occasionally experimented on Oxalis speoiosa, but until now have never found time to publish the results. In 1871 Hildebrand published an admirable papert in which he shows in the case of two species of Oxalis, that the sexual relations of the three forms are nearly the same as in Lythrum salicaria. I will now give an abstract of his o bservations, and afterwards of my own less complete ones I may premise that in all the species seen by me, the stigmas of the :five straight pistils of the long-styled form stand on a level with the anthers of the longest stamens in the two other forms. In the mid-styled uppermost anthers. The numerous stamens are graduated in length, and the pollen-grains from the longest and shorte-st ones did not present any marked difference in diameter. Therefore theBe species do not appear to be heterosty led. * 'Monatsber. der Akad. der Wiss. Berlin,' 186o, pp. 352, 372. He gives drawings of the three forms at p. 42 of hid 'GeschlechterVertheilung,' &c., 1867. t 'Bot. Zeitung,' 1871, pp. 416 and 432. |