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Show 328 OLEISTOGAMIO FLOvVERS. 0IIAP. VIII. we should remember that this is a naturalised species. The perfect flowers are usually barren in England; but Prof. Asa Gray writes to me that after Inidsummer in the United States some or many of them produce capsules. Impatiens noli-me-tan,qere.-l can add nothing of importance to Von Mohl' s description, excepting that one of the rudimentary petals shows a vestige of a nectary, as ·Mr. Bennett likewise found to be the case with I. fulva. As in this latter species all five stamens produce so1ne pollen, though small in a1nount; a single anther contains, according to \Ton Mohl, not 1nore than 50 grains, and these e1nit their tubes while still enclosed within it. The pollen-grains of the perfect flowers are tied together by threads, but not, so as far as I could see, those of the cleistogamic ~owers ; and a provision .of this kind would hero have been useless, as the grains can never be transported by insects. The flowers of I balsamina are visited by humble-bees,* and I am ahnost sure that this is the case with the perfect flowers of I. noli-1ne-tangere. From the perfect flowers of this latter species covered with a net eleven spontaneously self-fertilised capsules were produced, and these yielded on an average 3 ·45 seeds. Son1e perfect flowers with their anthers still containing an abundance of pollen were fertilised with pollen from a distinct plant ; and the three capsules thus produced contained, to my surprise, only 2, 2, and 1 seed. As I. balsamina is proterandrous, so probably is the present species; and if so, cross-fertilisation was effected by me at too early a period, and this may account for the capsules yielding so few seeds. . Drosera rotundifolia.-The first flower-stems w hwh * I:l. Muller, 'Die Befruchtung,' &c. p. 170. CHAP. VIII. OLEISTOGAMIO FLO.WERS. 329 were thrown up by some plants in my green-house bore only cleistogamic flowers. Th petals of small size remained permanently closed over the reproductive organs, but their white tips could just be seen between the almost completely closed sepals. The pollen, which was scanty in amount, but not so scanty as in Viola or Oxalis, remained enclosed within the anthers, whence the tubes proceeded and penetrated the stigma. As the ovarium swelled the little withered corolla was carried upwards in the form of a cap. These cleistogamic flowers produced an a bun dance of seed. Later in the season perfect flowers appeared. With plants in a state of nature the flowers open only in the early morning, as I have been informed by Mr. Wallis, who particularly attended to the time of their flowering. In the case of D. Anglica, the still folded petals on some plants in my greenhouse opened just sufficiently to leave a minute aperture; ·the anthers dehisced properly, but the .pollen-grains adhered in a mass to them, and thence emitted their tubes, which penetrated the stigmas. These flowers, therefore, were in an intermediate condition, and could not be called either perfect or cleistogamic. A few miscellaneous observations may be added with respect to some other species, as throwing light on our subject. Mr. Scott states* that Eranthemum ambiguum bears three kinds of flowers,-large, conspicuou~, open ones, which are quite sterile, -others of intermediate size, which are open and moderately fertile-and lastly small closed or cleistogamic ones, which are perfect! y fertile. Ruellia tuberosa, likewise one of the Acanthacere, produces both open and cleis- * ' Journal of Botany,' London, new series, vol. i. 1 872, pp. 161-4. |