304 COMMON TREES AND SHRUBS 



planted in its place and so becomes a common woodland 

 tree. It also tends to spread by self-sown seedlings. In 

 Scotland it is known as the Plane Tree, but it must not be 

 confused with the true Plane so commonly planted in 

 London, which is a form of Platanus acerifolia. 



It is a large tree, fifty to sixty feet high, with a wide- 

 spreading, somewhat pyramidal, crown. The ash-coloured 

 bark is smooth, and in the old tree scaly, but not fissured. 

 The terminal bud continues growth ; therefore branching 

 is monopodial. The buds are in crossed pairs (Fig. 70), the 

 terminal and also the flowering buds being larger than the 

 lateral buds. The branches are slaty-grey to reddish-brown, 

 and are dotted with numerous lenticels. The details of 

 a shoot, the structure of a bud, and the formation of the 

 leaf-mosaic have already been described (pp. 113-14, Figs. 

 70, 71, and 73). 



Beneath a Sycamore on the side of a road the pavement 

 is often covered with shining rain-like drops, due to a sticky, 

 sugary excretion called ' honey-dew ', from aphides which 

 infest the leaves. They suck the sap and exude drops of 

 honey-dew, which spread over the leaves like a varnish. 

 When the aphides are abundant, the drops fall from the 

 tree like fine rain. 



Two opposite buds are formed immediately below the 

 terminal one, and if the latter produces a flowering shoot 

 the axis ceases to grow in length. The flowering shoot is 

 eventually thrown off and leaves a scar between the two 

 lateral buds, which in time give rise to a forked branch 

 (false dichotomy). 



The flowers arise in large end buds. The inflorescence 

 (Fig. 202, 1) is a pendant raceme of umbel-like cymes, each 

 with three or four flowers opening in May or June. The 

 flowers vary in the raceme. Usually the terminal one of 

 a cyme (2) is complete, and consists of five sepals and 

 five petals all similar, greenish-yellow, and free. There 



