TREES AND SHRUBS. 403 



flower has a bell-shaped " calyx " with four to eight lobes, a 

 stamen opposite each lobe, and a two-chambered ovary with 

 two spreading stigmas (Fig. 170). At first the stigmas pro- 

 ject beyond the stamens and are receptive, but after a time 

 the filaments lengthen and carry out the anthers, which then 

 open. The pollen is carried by the wind ; it is obvious that 

 self-pollination is prevented during the female stage of the 

 flower, but it may occur when the anthers of the flower open 

 if cross-pollination has failed. 



The ovary becomes an akene, with a thin wing around the 

 seed-containing part ; the fruits (oval, notched above) are at 

 first green, but become brown and ripe by May. In Wych 

 Elm the seed is at the centre of the fruit (about 1 in. long) ; 

 in the smaller fruit of Common Elm (about i in. long) it is 

 above the centre. The seeds of Common Elm are said never 

 to germinate in this country, but this is largely atoned for 

 by the fact that this species of Elm sends up numerous 

 suckers from its roots, so that one often sees a long stretch 

 of hedge on each side of an old Elm, or a thicket of young 

 Elms around the parent tree. The Common Elm is not 

 regarded as a native British tree, but as having been intro- 

 duced within historic times. The "Wych Elm, regarded as 

 native, does not produce suckers, as a rule, unless the tree is 

 cut down ; its winged akenes (samaras) are well adapted for 

 wind-dispersal, and in germination the green cotyledons are 

 carried into the air. 



Common Elm differs from Wych Elm chiefly in having 

 smaller leaves, flowers, and samaras ; fewer " calyx "-lobes 

 and stamens ; in the non-germination of its seeds in Britain, 

 and its production of suckers in large numbers from the 

 roots ; in the direction of growth of its main branches and 

 the shape of the crown. 



392. Sycamore Maple or False Plane (Acer pseudo- 

 platanus), usually called simply Sycamore (though this name 

 was originally given to a wild Tig, Ficus sycomorus, growing 

 in the East), is not a native of Britain, though so common 

 here ; its home is in central Europe and western Asia. The 

 Sycamore is really a species of Maple ; the only native British 

 species of Acer is the Field or Hedge Maple (A. campestris), 

 but two other species are commonly grown Norway Maple 



