Fig. 100.—Spike of Carex acuta, with female flowers at the summit.
On the subject of this section the reader may consult A. Braun,. 'Das Individ.,' 1853, p. 65. Caspary, 'De Abietin. flor. fem. struct. morphol.' Schleiden. 'Principles,' English edition, p. 299. Mohl, 'Verm. Schrift.,' p. 45. Meyen in 'Wiegm. Archiv.,' 1838, p. 155. Cramer, 'Bildungsabweich,' p. 4, tab. v, figs. 13–17. Parlatore, 'Ann. Sc. Nat.,' ser. iv, vol. xvi, p. 215, tab. 13a. See also under the head of Prolification, Substitutions, &c.
Change from the monœcious to the diœcious condition.—This is of less frequent occurrence than might have been anticipated. In the 'Gardeners' Chronicle,' 1847, pp. 541 and 558, several instances are noted of walnut trees bearing female flowers to the exclusion of males. The mulberry tree has also been noticed to produce female blossoms only, while in other plants male flowers only are developed.
It seems probable that the age of the plant may have something to do with this production of flowers of one sex to the exclusion of the other.
Change from the diœcious to the monœcious condition.—Androgynism.—This is of far more common occurrence than the preceding.
Fig. 101.—Monœcious inflorescence of Hop.
In the hop (Humulus Lupulus), when monœcious, the female catkins are usually borne on the ends of the branches as shown in the cut (fig. 101), and a similar thing has been noticed in Urtica dioica by Clos, 'Bull. Soc. Bot. France,' vol. 9, p. 7.