404 



TREES AND SHRUBS. 



Fig. 171. The Sycamore, with 

 Flowers. 



(A. platanoides) and Ash-leaved Maple (A. negundo). 

 They all have the leaves in crossed pairs (therefore in four 

 rows, decussate arrangement) and a fruit which splits into 



two (sometimes three) winged 

 akenes. 



The Sycamore Maple (Fig. 

 171) is a fairly tall tree (up to 

 60 ft.) ; the bark long remains 

 smooth, but eventually becomes 

 rough and scaly. Each leaf has 

 a stalk whose broad base extends 

 about half round the stem ; the 

 blade (4 to 8 ins. broad) has five 

 pointed toothed lobes and is 

 shiny and dark-green above, 

 dull and light-green below. 

 The main veins spread out 



from the top of the stalk, one running to each lobe and 

 giving off side veins; in the young leaf the veins are 

 fringed below with hairs, but in the old leaf the hairs are 

 confined to tufts at the points where the secondary veins 

 join the five main veins. 



On a horizontal branch the leaves are arranged so that 

 the blades may get as much light as possible ; the leaf stalks 

 vary in length, and those of the upper and lower rows of 

 leaves become twisted, while the blades vary in size, in 

 amount of lobing and sizes of the lobes, so as to produce an 

 effective leaf-mosaic. On a more or less horizontal branch 

 the buds (Art. 177) on the upper and lower sides either 

 remain dormant or grow into very short shoots, so that on 

 an old branch of this kind the long twigs are confined to 

 the flanks ; but on more erect branches there are strong 

 twigs on all sides, especially on the side farthest from the 

 middle of the tree. How may these facts be explained ? 



A flowering shoot (how can you tell in winter which buds 

 contain an inflorescence ?) bears one or two pairs of leaves 

 and ends in a long hanging bunch of stalked green flowers. 

 At the base of the inflorescence branches bearing each about 

 three flowers arise from the axis, but higher up it gives off 

 single flowers. Note the five sepals, the five petals (narrower 

 than the sepals), the stamens (8 to 12) inserted on a yellow 



