[Illustration: FIG. 324.--_Alnus glutinosus._ Branch of Alder with ♂-(_n_) and ♀-(_m_) catkins: _k_ bud; _b_ fruit-bearing catkin (“cone.”)] _Alnus_ (Alder) (Figs. 324–326). In the majority of species the ♂-and ♀-catkins are both developed in the year previous to their flowering, and pass the winter naked and bloom before the leaves expand. ♂-flower: 4 stamens. ♀-flower: the 5-lobed cover-scales of the ♀-catkin are woody and remain attached to the axis, so that the entire catkin when ripe resembles a small cone (Fig. 324 _b_). Each cover-scale supports two winged or wingless nuts. ~In the native species of Alder the buds are stalked (Fig. 324 _k_). The bud-scales are formed by the stipules of the lowest leaves.~ _Betula_ (Birch). The ♂-catkins, in the native species, appear in autumn, the ♀-catkins in the flowering year on leaf-bearing, short-lived shoots. ♂-flowers: 2 stamens, divided (Fig. 328 _A_). The 3-lobed cover-scales (Fig. 327 _a_) of the ♀-catkin are detached from the axis; each cover-scale supports 3 broadly winged nuts (_b_). ~The stem has cork with annual rings. The young twigs and leaves have aromatic resin glands.~ [Illustration: FIG. 325.--_Alnus glutinosa_: _A_ dichasium of ♂-flowers seen from the front; _B_ the same from inside; _C_ the same from the back; _D_ dichasium of ♀-flowers with subtending-leaf and four bracteoles. The letters _b_, α, β, β′, β are the same as in Fig. 326 _A_.] [Illustration: FIG. 326.--_Alnus glutinosa_: diagram of dichasia of ♂ (_A_) and ♀ (_C_) catkins; _B_ a cone-scale. All the bracteoles in _A_ and _C_ are slightly pressed from their normal position.] THE INFLORESCENCES OF THE ALDER.--In the axil of each cover-scale [_b_ in the Figs] is situated, in the ♂-catkins (Figs. 326 _A_, 325 _A-C_) a 3-flowered dichasium, the flowers of which have a 4-partite perianth, the posterior perianth-segments being sometimes almost suppressed, and 4 stamens with undivided filaments. In the ♀-catkin (Figs. 325 _D_, 326 _C_) a 2-flowered dichasium is found, the middle flower being suppressed (indicated by a star in _C_). In both instances the inflorescences have two bracteoles (α-β) and the flowers borne in their axils have each one bracteole (β′), the other one (α′) being suppressed and therefore in 326 _A_ and _C_ only represented by a dotted line; these four bracteoles unite with the cover-scale (_b_) which supports the entire dichasium, to form the 5-lobed “cone-scale” (Fig. 326 _B_) which in the ♀-catkin eventually becomes woody. THE INFLORESCENCES OF THE BIRCH.--A 3-flowered dichasium is situated in the axil of the cover-scale in both ♂-and ♀-catkins (Fig. 328 _A_, _B_); only the central flower has bracteoles (α-β) (the lateral flowers having no bracteoles), and these bracteoles unite, as in the Alder, with the supporting cover-scale (_b_), and form a three-lobed cone-scale (Fig. 327 _a_).