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Show 322 CLEISTOGAMIC FLOWERS. CHAP. VIII. remaining five contained on an average 10·0 seeds per capsule. This is rather above the average 9·2, which eleven capsules from perfect flowers fertilised with their own pollen yielded, and. considerably above the average 7 ·9, from the capsules of perfect flowers fertilised with pollen from another plant; but this latter result must, I think, have been accidental. Hildebrand, whilst searching various Herbaria, observed that many other species of Oxalis besides 0. acetosella · produce cleistogamic flowers ; * and I hear from him that this is the case with the heterostylecl trimorphic 0. incarnata from the Cape of Good Hope. Oxalis (Biophytum) sensitiva.-This plant is ranked by many botanists as a distinct genus, but as a subgenus by Bentham and Hooker. Many of the early flowers on a mid-styled plant in my hot-house did not opeli properly, and were in an intermediate condition between cleistogamic and perfect. Their petals varied from a mere rudiment to about half their proper size; nevertheless they produced capsules. I attributed their state to unfavourable conditions, for later in the season fully expanded flowers of the proper size ap· peared. But Mr. Thwaites afterwards sent me from Ceylon a number of long-styled, mid-styled, and short· styl'ed flower-stalks preserved in spirits; and on the same stalks with the perfect flowers, some of which were fully expanded and others still in bud, there were small bud-like bodies containing mature pollen, but with their calyces closed. These cleistogan1ic flowers do not differ much in structure from the perfect ones of the corresponding form, with the exception that their petals are reduced to extremely minute, barely visible scales, which adhere firmly to the rounded * 'Monatsbericht'der Akad. der Wiss. zu Berlin,' 1866, P· 369· CHAP. VIII. OXALIS. 323 bases of the shorter stamens. Their stigmas are much less papillose, and smaller in about the ratio of 13 to . 20 divisions of the micrometer, as measured transversely from apex to apex, than the stigmas of the perfect flowers. The styles are fJirrowed longitudinally, and are clothed with simple as well as glandular hairs, but only in the cleistogamic flowers produced by the long-sty led and mid -sty led forms. The anthers of the longer stamens are a little smaller than the corresponding ones of the perfect flowers, in about the ratio of 11 to 14.. They dehisce properly, but do not appear to contain much pollen. Many pollen-grains were attached ?Y short .tubes to the stigmas ; but many others, still adhenng to the anthers had emitted their tubes to a considerable leno·th ,;ithout havino- . . . b ' b come In contact .with the stigmas. Living plants ought to be examined, as the stigmas, at least of the l~n.g-style~ form, pro)ect beyond the calyx, and if Vl~Ited by Ins~c~s ( wh~ch, however, is very improbable) m1ght be fe.rtihsed with pollen from a perfect flower. The most singular fact about the present species is that long-styled cleistogamic flowers are produced by the long-styled. plants,. and mid-styled as well as short-sty led cleistogamic flowers by the other t !:r:s; so th~t there are three kinds of cleistogan:~ thre~ lnnds of perfect flowers produced by this ~ne I ~peCies ! Most of the heterosty led species of i]~a ~:.are more o~ .less sterile, many absolutely so if It ~gi ~mately fertilised with their own-form poll~n Is. t fler~fore probable that the pollen of the cleisto-· gamic owers has bee d'fi d . on their . n mo 1 e In power, so as to act seed own stigmas, for they yield an abundance of flo s. We .m~y perhaps account for the cleistogamic wers consisting f th th .r ci l o e ree lOrms, through the rin-p e of correlated growth, by which the cleistog~mic y 2 |