164 YOUNG DICOTYLOUS TREES 



which acquire very different shapes as the leader is lost 

 and the crowns become rounded off at the top. Among 

 these may be mentioned the Oaks, Plane, Elms, Lime, 

 Alder, Birch, Hornbeam, Beech, Chestnut, Walnut, Willows 

 and Poplars, all with their young branches arranged alter- 

 nately and spirally round the main stem ; further the 

 Horse-chestnut, Maples, Ash, &c., all with the young 

 branches and twigs opposite and decussate. None of them 

 retain the tapering pyramidal form for long, but as the 

 leader dies off, or slows down in its growth, the branches 

 below rapidly assert themselves, and many of the twigs in 

 the interior of the crown die off, producing the irregularity 

 of form so well known in these round-headed as opposed 

 to pointed trees. 



It would occupy too much space to describe these 

 transient forms of trees, from 10 20 feet or so in height, 

 in further detail here. Those cases in which the pyra- 

 midal form is retained longer will be found below : the 

 others must be sought for among the round-headed trees. 

 When leaves and flowers are present the discrimination is 

 easy; when absent the diagnosis may have to be sought 

 for in the Section on Buds, &c. The Beech is apt to retain 

 the pointed-ovoid or pyramidal form for some time. 



** Crown rounded at the apex, broadest at 

 the base or near the middle. General 

 shapes oblong, ellipsoid, ovoid or obovoid, 

 dome-shaped or more or less spheroidal. 



[For (ft) t Bark not rugged with conspicuous deep longi- 



see p. 182.] tudinal fissures or rough ridges ; smooth for 



a long time on the limbs, and often on the 



trunk. 



[For (OO) Bark, or superficial periderm, whitish-grey 



seep. 170.] t slaty-grey, persistent and smooth, even 



on the trunk; limbs and principal branches 



