342 



DICOTYLEDONES. 



FIG. 325. Alnus glutinosa: A dicha^ium of rf -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 

 liracteoles. The letters b, a, ft, ft', ft, are the same as in Fig. 



324 ?>). 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 

 autnmn, 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 sup- 

 ports 3 broadly- 

 winged nuts (6). 

 The stem has cork 

 with annual rings. 

 The young twigs and 

 leaves have aromatic 

 resin glands. 



THE INFLORESCEN- 

 CES 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 (ct-/3) and the 

 flowers borne in their axils have each 

 one bracteole ('), the other one (a') be- 

 ing suppressed and therefore in 326 A 

 and C only represented by a dotted 

 line ; these four bracteoles unite with 

 the cover-scale (6) 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 <J- 

 and ? -catkins (Fig. 328 A,B)', only the 

 central flower has bracteoles (a-/J) (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). 



FIG. 326. Alnna gluiinosa: diagram 

 of dicbasia of <J (A) and ? (C) catkins; 

 B a cone-scale. All the bracteoles in A 

 and C are slightly pressed from their 

 normal position. 



