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Show 310 CLEISTOGAMIC FLOWERS. CHAP. VIII. CHAPTER VIII. 0LEISTOGAMIC FLOWERS. General character of cleistogamic flowers-List of the genera prollucing such flowers, and their distribution in the vegetable series-Viola description of the cleistogamic flowers in the several species, thei; fertility 9ompared with that of the perfect flowers-Oxalis acetosella-0. sensitiva, three forms of cleistogamic flowers- Vandellia- Ononis-Impatiens-Drosera-Miscellaneous observations on various other cleistogamic plants-Anemophilous species producing clei:::.togamic flowers-Leersia, perfect flowers rarely developed --Summary and concluding remarks on the origin of cleistogumic flowers-The chief conclusions which may be drawn from the observations in this volume. IT was known even before the time of Linnceus that certain plants produced two kinds of flowers, ordinary open, and minute closed ones; and this fact formerly gave rise to warm controversies about the sexuality of plants. These closed flowers have been appropriately named cleistogamic by Dr. Kuhn.* They are remarkable froin their small size and from never opening, so that they resemble buds; their petals are rudimentary or quite aborted; their stamens are often reduced in number, with the anthers of very small size, containing few pollen-grains, which have remarkably thin transparent coats, and generally emit their tubes whilst still enclosed within the anthercells; and, lastly, the pistil is much reduced in size, with the stigma in some cases hardly at all developed. These flowers do not secrete nectar or emit any odour; fron1 their small size, as well as from the corolla being rudimentary, .they are singularly inconspicuous. Con· * 'Bot. Zeitung,' 1867, p. 65. CHAP. VIII. CLEISTOGAMIC FLOWERS. 311 sequently insects do not visit them; nor if they did, could they find an entrance. Such flowers are therefore invariably self-fertilised; yet they produce an abundance of seed. In several cases the young capsules bury themselves beneath the ground, and the seeds are there matured. These flowers are developed before, or after, or simultaneously with the perfect ones. Their development seems to be largely governed by the conditions to which the plants are exposed, for during certain seasons or in certain localities only cleistogamic or only perfect flowers are produced. Dr. Kuhn, in the article above referred to, gives a list of 44 genera including species which bear flowers of this kind. To this list I have added some genera, and the authorities are appended in a foot-note. I ~ave omitted three names, from reasons likewise given 1~ th~ foot-note. But it is by no means easy to demde In all cases whether certain flowers ought to be ranked as cleistogamic. For instance, l\ir. Bentham informs me that in the South of France some of the flo~ers on the vine do not fully open and yet set fr~It .; and I hear from two experienced gardeners that this Is the case with the vine in our hot-houses; but as the flo':ers do not appear to be completely closed it would be Imprudent to consider them as cleistogamic. ~he flowers of some aquatic and Inarsh plants, for Instance of Ranuneulus aquatilis Alisma natans Subu.l aria, Illecebrum ' Menyanthes' , and E uryaI e, ~ rema1n closel~ sh~t as long as they are sub-merged, and In this condition fertilise themselves. *_Delpino,' Sull'Opera, laDistribuziOne dei Ses:si neUe Piante '&c 1867 ' P· 30 · su b ulan.a , how'e ver,. sometimes has its flowers fully e~panded be~leath the water, see Su J. E. Smith, 'English Flora,' vol. i~i. 1825, p. 157. For the behavwur ofMenyanthes in Russia see Gillibert in 'Act. Acad. St. Petersb.,' 1777, part ii. p. 45.-0n Euryale, 'Gardener's Chronicle, 1877, p. 280. ' |