QUERCtFLORJ:. 



341 



It is worthy of remark thcit in Betnlacea;, Conjlacea and Quercus the ovules, 

 and to some extent the loculi of the ovary are not developed till after pollin- 

 jition, so that the development of the pollen-tube proceeds very slowly. The 

 smallness of the flowers, the absence of honey, the dryuess and lightness of tht 

 pollen, the size of the stigma and the abundance of hairs found on many 

 stigmas are all adaptations for wind-pollination. It is also an advantage that 

 the flowers are generally pollinated before the foliage-leaves are developed, thug 

 preventing the pollen being entangled by the leaves. 



The two orders Betulacece and Conjlaceie mentioned here are by other authors 

 united into one order. [It is doubtful whether these two should be retained in 

 the family Querciflorte, as recent researches (p. 273) have shown that they 

 differ from the Cupulifera in many important points, and agree with tbo 

 Casuarinas in the fact that the pollen-tube enters the ovule through thu 

 chalaza.] 



Order 1. Betulaceae (Birches). Monoecious, with thick, 

 cylindrical, compound $ and ? inflorescences (2- or 3-flowered 

 dichasia in a spike with 

 spirally- placed floral- 

 leaves) (Figs. 324, 326, 

 328). When the perianth 

 in the ^ -flower is com- 

 pletely developed, it is 

 composed of 4 somewhat 

 united leaves, which are 

 placed opposite the 4 

 stamens (Figs. 325, 326 A). 

 The female flowers are 

 naked ; the ovary is bi- 



locillar, with two Styles FlG 3M ._ 4llMW glut( : nosits . Branch of Alder with 



(J-(n) and <j>-(m) catkins: k bud ; It fruit-bearing 

 catkin ("cone.") 



TV 



and one pendulous ovule in 

 each loculus. The sub- 



tending floral-leaves unite with the bracteoles and form a 3-5-lobed 

 cover-scale, which is not attached to the fruit (Figs. 325 D, 326 J3). 

 Fruit a nut without cupule (see Corylacece and GupuUferce). In the 

 bud the leaves are flat. The stipules are deciduous. On germination the 

 cotyledons are raised above the ground. Terminal buds are only found on old 

 Alder trees ; the Birch has svmpodial branches. 



Alnus (Alder) (Figs. 324-326). In the majority of species the 

 (J- 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. 



