CLEISTOGAMY 51 



algerica (Battandier, Bui. soc. bot., Paris, xxx), Brassica nigra (Todd, Amer. Nat., 

 Boston, XV, 1 881), Erythraea Centaurium (A. S. Wilson, Brit. Ass. Rep., 1878), and 

 Anchusa officinalis (E, Warming, Bot. Tids., Kjobenhavn, xvii, 1877). I myself 

 always found the last three species homostylous. 



VI. Cleistogamy ^ 



Hugo von Mohl in his memoir, ' Einige Beobachtungen iiber dimorphe Bluten ' 

 (Bot. Ztg., Leipzig, xxi, 1863, pp. 309 et seq.), mentions a number of plants bearing 

 on the same stock some flowers that open normally and also others that do not 

 open at all. The corolla of such flowers is reduced or absent, while stamens and 

 pistil are in some respects well developed. Healthy fruits result from the self- 

 fertilization that takes place in the permanently closed bud-like flowers. A few 

 years later Kuhn (Bot. Ztg., xxv, 1867, pp. 65-7) published a further and exten- 

 sive list of such plants, and introduced the term deisiogamous to designate the 

 permanently closed flowers. 



According to H. v. Mohl (Bot. Ztg., xxi, 1863), Dillenius was probably the 

 first to discover cleistogamous flowers on the plant subsequently named Ruellia 

 clandestina by Linnaeus (Hort. Eltham., 1732, p. 328, Fig. 320). Viola mirabilis 

 was the second plant in which Dillenius observed this phenomenon: he found 

 that the spring-flowers with well- developed corolla and fully formed reproductive 

 organs rarely produce fruit, while the later flowers devoid of corolla do so regularly. 



In many parts of his writings Linnaeus speaks of cleistogamous flowers, and proves 

 that in these small blossoms the want of stamens and carpels is only apparent. 



Our knowledge of cleistogamous flowers was further extended by the observa- 

 tions of: Schkuhr, Hegetschweiler, De CandoUe, Du Petit Thouars, L. C. 

 Richard, Adrien de Jussieu, Aug. St. Hilaire, Bentham, Torrey and Asa Gray, 

 Spach, Weinmann, Wight, Weddell, Maximowicz, Daniel Miiller, Brongniart, 

 Michalet, and others. H. v. Mohl's (op. cit., pp. 321-8) researches finally gave us 

 a clear view of these remarkable flowers. 



Hugo von Mohl's classical account of the cleistogamous flowers of Oxalis 

 Acetosella (Bot. Ztg., 1863, pp. 321, 322) is somewhat as follows. In the second 

 week of June, when the fruits of the spring-flowers possessing corollas contained 

 ripe seeds (at Tiibingen), there were large numbers of small flowers in all stages 

 of development up to the complete maturation of fruit. They usually occurred 

 on plants which had developed one or several spring-flowers in the axils of the upper 

 leaves, but were also occasionally present on plants devoid of spring-flowers. These 

 summer-flowers and fruits are distinguished very easily from the spring-flowers by 

 the different length and direction of the flower-stalk. The stalk of the spring-fruit 

 has a length of about three inches, is straight, and possesses a joint bearing two 

 bracteoles, about half-way down. The peduncle of the small flower, on the other 

 hand, is only about four lines long (i'^'= about 2^ mm.), and bent like a hook 

 at the top, while its joint is only ^i line from the flower. The latter, owing 

 to the shortness of the flower-stalk, is hidden in the moss and pine-needles among 



^ [See K. Goebel, ' Die kleistogamen Bluten und die Anpassungstheorie,' Biol. Centralbl., 

 Berlin, xxiv, 1904, for the most recent exposition of cleistogamy. Ed.] 



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