CATKIN-BEARING TREES 291 



Beech, forming tiers of mosaics facing the sky, produce 

 a closer canopy and cast a deeper shade than any other 

 British tree, and the vegetation beneath is very scanty. 

 As regards light, it stands at the opposite extreme to the 

 Birch : it is a shade-enduring tree. 



The flowers are in heads, which arise in the axils of the 

 leaves of the current year, and therefore come out after 

 the leaves. The stamens and pistils are in separate flowers 

 on the same tree (Fig. 191, 2). The male flowers are in 

 a globular cluster at the end of a long, pendulous stalk. 

 Each flower has a perianth of four to seven hairy lobes 

 (3), and from eight to twelve stamens. The female flowers 

 (4) arise higher on the branch ; the stalks are short, 

 thick, and erect ; and each inflorescence contains only 

 two flowers. A single flower consists of a three-celled 

 ovary with two ovules in each cell, and three red stigmas. 

 On the top of the ovary is a perianth with about six lobes. 

 Surrounding the two flowers is a hairy cupule, which, after 

 fertilization, becomes thick, woody, and spiny (5), and 

 when ripe splits into four valves. One nut is formed in 

 each flower; it is triangular, with a smooth brown coat, 

 and contains only one seed. 



Oak 



The Oak (Fig. 192) is the largest and most characteristic 

 of British trees, and formerly Oak forests covered a large 

 part of England. Two species are common, and they 

 sometimes characterize distinct habitats. The Sessile Oak 

 (Quercus sessiliflora) is the dominant tree on shallow, poor 

 siliceous soils, and is typical of the woods on the Pennine 

 slopes, and other similar hilly regions. The Peduncled 

 or Stalked Oak (Q. Robur) is often the prevailing tree in 

 lowland woods, with a deep rich siliceous soil over clays 

 and loams. On soils containing much lime, both species 

 tend to occupy a very subordinate place in the vegetation. 



t 2 



