238 ALDER 



4 small bracteoles ; all the bracteoles become fused to the 

 scale, making it a complex scale with 5 lappets. 



The $ catkin 3 4 up to 5 10 mm. long, smooth, 

 with red-brown stigmas; becoming ovoid, stiff, and cone- 

 like, 10 13 mm. long, with sticky resinous wax, passing 

 to smooth. The shield-like end of the scale violet-brown, 

 with a central pale brown point, almost like an apophysis 

 and its umbo. Each scale of the $ catkin bears 2 flowers 

 with no perianth (achlamydeous), and consisting of a flat 

 2-chambered and 2-ovuled ovary with 2 stigmas, ripening 

 to a one-seeded achene, rimmed at the margin. Here, 

 however, the scale, with its fused bracteoles, persists as a 

 dark woody structure, and the ovoid old " cones " are very 

 characteristic in winter. They differ from true cones in 

 having complex scales, in bearing filamentous stamens and 

 simple pollen, and especially in having a perianth to the <g 

 flower, and a true ovary with stigmas and enclosed ovules 

 (angiosperm). 



On comparing the morphological diagram of Betula 

 (Fig. 73, p. 235), it will be seen that Alnus differs chiefly 

 in having a more complete perianth to each of the </ 

 flowers, which are 4-stamened, and in minute points 

 regarding the bracteoles, and in having lost the central 

 flower of the dichasium in the $ flower, also with small 

 differences in the bracteoles. Pollen with 5 germ-pores, 

 pale yellow, polyhedral with rounded angles, smooth, about 

 31 p. 



[The Plane has its monoecious flowers, both </ and $ , 

 in globular heads (capitula), sessile at intervals, on long, 

 pendent stalks; these are not true catkins, however, if 

 only because the flowers are dichlamydeous. The tree 

 is readily distinguished by its large palmate leaves, 

 with buds buried in the bases of the petioles. See p. 

 273.] 



