XENOGAMY 



43 



The discoverer of Dichogamy (Sprengel, 'Entd. Geh,,' p. 19) named the two 

 cases of this phenomenon male-female (Androgyna), and female-male (Gynandra). 

 These two technical terms cannot, however, be used here, since Linnaeus employed 

 them in other connections. Hildebrand, in 1867 (' Geschlechterverteilung,' p. 16), 

 introduced the expressions Protandry and Protogyny, which would have been 

 universally accepted by botanists as being suitable, had not the forms Proterandry and 

 Proterogyny, employed by Delpino in 1868 and 1875 (' Ulteriori osservazioni,' i and 

 ii), been still more widely adopted. Kirchner, in 1888 ('Flora von Stuttgart,' p. 39, 

 note), called attention to the fact that Hildebrand's terms are preferable because shorter 

 and more convenient, while grammatically quite as correct as those of Delpino '. 



Dichogamy is by no means limited to individual flowers, for probably all 

 monoecious and most dioecious plants are dichogamous. All the former appear 

 to be protogynous, i. e. the female flowers of a plant mature before the male, and this 

 lime-difl'erence in the development of the sexes often amounts to several days. Thus, 

 the female flowers of Alnus viridis are mature four or five days before the male, 

 those of Typha minima as much as nine days, while according to Kerner (' Nat. 

 Hist. PI.,' Eng. Ed. i, II, p. 313), in the case of alders, birches, elms, oaks, beeches, 

 hazels, planes, and the walnut, the difference amounts to two or three days. Accord- 

 ing to my own observations, the difference, especially in the case of Corylus avellana, 

 may be much greater under certain circumstances. If, in particular, an unfavourable 

 rainy or cold period sets in, after the protrusion of the stigmas, the discharge of 

 pollen is considerably delayed. 



Most dioecious plants are also protogynous. According to Kerner (op. cit.) 

 the female flowers of many willows are mature several days before the male, in 

 spite of the fact that the male trees are subject to the same conditions of life as 

 the female ; they grow in the same ground, are exposed equally to sunlight, and 

 encounter the same currents of air. Again, according to Kerner, the stigmas of 

 the female flowers of Salix amygdalina are ready for pollination two or three days 

 before the anthers of the male flowers dehisce. The same holds for S. purpurea, 

 viminalis, and fragilis, while the willows of the lower Alps (S. herbacea, retusa, 

 and reticulata) usually present a difference of one day only in the development 

 of the two kinds of flowers. In Cannabis sativa, the difference amounts to four 



' As these terms will be much used in botanical instruction in secondary schools, efforts have 

 been made to find suitable German equivalents for them. W. Behrens in the first edition of 

 his ' Lehrbuch der Allgemeinen Botanik ' spoke of ' mannlich-weiblich ' (male-female) (o-o) and 

 ' weiblich-mannlich ' (female-male) (O-J) ways of flowering, thus making use of Sprengel's original 

 terms. [The latter symbol is the long-recognized one for monoecious and is incorrectly introduced in 

 the sense of the text by Behrens, and reproduced in the English edition of his textbook.' Ed.] 

 He retained these expressions in his second edition (1882, p. 182), but in the third edition of his 

 textbook he introduced ' vormannlich ' and * vorweiblich ' [i.e. male first and female first], as 

 proposed by Hildebrand. E. Nichel (Bot. Centralbl., Cassel, xlix, 1892, pp. 10, 11) suggested the 

 terms ' poUenvorreif ' or ' narbennachreif ' [i.e. pollen first ripening or stigma last ripening], and 

 ' narbenvorreif ' or ' poUennachreif ' [i. e. stigma first ripening or pollen last ripening] , and for 

 monogamous the term ' zwitterreif ' [i.e. bisexual ripening]. I would replace these (op. cit., Hi, 

 pp. 217, 218) by the terms 'staubblattvorreif and ' fruchtblattvorreif ' [i.e. stamen first ripening and 

 carpel first ripening], but at the same time maintain that the terms Proterandry and Proterogyny should 

 be applied as a matter of course by scientific botanists, and as international terms. [In Britain the 

 scientific terms protandry or proterandry and protogyny or proterogyny are in general use. Ed.] 



