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Show 330 CLEISTOGAMIC FLOWERS. CHAP. VIII. togamic flowers; the latter yield from 18 to 24, .whilst the former only fron1 8 to 10 seeds ; these tw? kinds of flowers are produced simultaneously, whereas In several other me In bers of the family the cleistogamic ones appear only during the hot seas?n. .i\ .. c~ording to Torrey and Gray, the North Amen can species of Helianthemum, when growing in poor soil, produce only cleistogamic flowers. The cleistogamic flowers of Specularia perfoliata are highly remarkable, as the! are closed by a tympanum formed by the rudimentary corolla, and without any trace o.f an opening. The stamens vary from 3 to 5 In number, as do the sepals.* The collecting hairs on the pistil, which play so important a part in the fertilisation of the perfect flowers, are here quite absent. Drs. Hooker and Thomson statet that some of the Indian species of Campanula produce two kinds of flowers; the smaller ones being borne on longer peduncles with differently formed sepals, and producing a more globose ovary. The flowers are closed by a tympanum like that in Spe.cularia. Some of the pl.ants produce both kinds of flowers, othG)rs only one k1~d; both yield an abundance of seeds. Professor Ohver adds that he has seen flowers on Oampanula colo1·ata in an intermediate condition between cleistoga1nic and perfect ones. . The solitary almost sessile cleistogamic flowers pro· duced by Monochoria vaginalis are differently prot~ct~d from those in any of the previous cases, namely, w1thm " a short sack formed of the n1em branous spathe, * Von Mohl, 'Bot. Zeitung,' 1863, pp. 314 and 323. Dr. Brom· field (' Phytologist,' vol. iii. p. 530) also remarks that the calyx of the cleistogamic flowers is usually only 3-cleft, while that of the perfect flower is mostly 5-cleft. , 1 ii t ' Journal Linn. Soc. vo · : 1857, P· 7. See al~o Prof~s~I, Oliver in 'Nat. Hist. ReVle ' 1862, p. 240. CHAP. VIII. CLEISTOGAMIC ]~LO,VERS. 331 ~ithout ar:y opening or fissure." There is only a single fertile stamen ; the style is almost o bs lete with the three stigmatic surfaces directed to one ide: Both the perfect and cleistogamic flowers produce seeds.* The cleistogamic flowers on some of the MalpighiaceEe seem to be more profound! y modified than those in any of the foregoing genera. According to A. de J ussieu t they are differently situated from the perfect flowe ·s; they contain only a single stamen, instead of 5 or 6; and it is a strange fact that this particular stamen is not developed in the perfect flowers of the same species. The style is absent or rudimentary; and there are only two ~varies instead of three. Thus these degraded flowers, as J ussieu remarks, "laugh at our classifications, for the greater number of the characters proper to the species, to the genus, to the family, to the class disappear." I may add that their calyces are not glandular, and as, according to Kerner,t the fluid secreted by such glands generally serves to protect the flowers from crawling insects, which steal the nectar without aiding in their cross-fertilisation, the deficiency of the glands in the cleistogamic flowers of these plants may perhaps be accounted for by their not requiring any such protection. As the Asclepiadous genus Stapelia is said to produce cleistogamic flowers, the following case may be worth giving. I have never heard of the perfect flowers of Hoya carnosa setting seeds :in this country, but some capsules were produced in 1\Ir. Farrer's hot-house ; * Dr. Kirk,' Journ. Linn. Soc.' vol. viii. 1864:, p. 147. ... t 'Archives du Museum,' tom. 111. 1843, pp. 35-38, 82-86, 589' 598. t 'Die Schutzmittelder Bliithen gegen unberufene Gaste,' 1876, p. 25. |