Fig. 330.—Diagrams of the ♂-flower (A) of Corylus and the dichasium of the ♀-flowers (B).
Fig. 331.—Nut of the Hornbeam with cupule.
Order 3. Cupuliferæ. Monœcious. The inflorescences make their appearance with the leaves, arising in the axils of the leaves of the same year. A woody cupule furnished externally with scales or spines is common, and surrounds 1-several flowers (the cupule in the Corylaceæ never encloses more than a single flower or fruit). The ♂-flower has a united perianth, which is, however, 4–6 partite, and encloses an indefinite number of undivided stamens. The ♀-flower has a superior, 6-merous perianth (3 + 3, compare Figs. [332] D, [334]); the gynœceum is formed of 3 (or in Castanea 4–6) carpels with a corresponding number of stigmas (Figs. [332] D, H; [334], [335]); and the ovary has at the base 3 (-6) loculi (Fig. [333]), each of which has 2 pendulous anatropous ovules; the fruit is a one-seeded nut (Figs. [332] H, [336]).
The cupule of the Cupuliferæ, according to the opinion of Eichler, is formed by united bracteoles, (compare Fig. [333], where the four valves in the cupule of Castanea are considered as bracteoles of the lateral flowers of the dichasium); according to another view (see Prantl, in Engler’s Bot. Jahrb., viii., 1889), it is a ring-like axial outgrowth independent of the bracteoles of the flower, whose scales and spines are floral-leaves. The cupule in the Oak only encloses the base of the fruit, but in the Eating-chestnut and Beech the fruit is completely enclosed, and consequently the cupule must divide into a number of valves (generally 4) to allow the fruit to escape. In the 3-flowered dichasia of Pasania, Sect. Eupasania (Trop. Ind.), each individual flower has its own cupule of the same structure and development as in Quercus; and, moreover, each group of flowers has externally the typical six bracteoles.
Fig. 332.—Castanea vesca: A branch with inflorescences; B ♂-flower; C young cupule with three ♀-flowers; D ♀-flower; E the same in longitudinal section; F cupule with 3 nuts (diminished); G, H nuts (G in longitudinal section to show embryo).
Castanea (Eating-chestnut, Fig. [332]). The catkins are erect (A), cylindrical, with the ♀ at the base and the ♂ at the top, or some are entirely ♂ and composed of small dichasia. The cupule (C, F) is 4-valved, provided with spines, and entirely envelops the 3 nuts; it is already developed at the time of flowering.—♂-flowers are most frequently borne in 7-flowered dichasia, and have a well developed perianth, most frequently consisting of 6 leaves in two whorls (Fig. [332] B), and a large number of stamens. ♀-flowers are most frequently borne in 3-flowered dichasia (Figs. [332] C, [333]); the letters in Fig. [333] indicate the older theory, according to which the 4 bracteoles (α′-β′) of the two lateral flowers are thick and united into a single 4-valved, woody cupule, which surrounds the 3 nuts, and is furnished externally with spines; the spines are well developed hair-structures.—6 carpels in two whorls.—The leaves in the vertical shoots have a divergence of 2/5, 3/8, 5/13; on the horizontal shoots they are alternate. The cotyledons remain underground on germination.
Fig. 333.—Diagram of the cupule of Castanea.