TREES OF THE NORTHERN UNITED STATES 



with the observation of trees, will soon teach the student 

 what constitutes a leaf. 



ARRANGEMENT. There are several different ways in 

 which leaves are arranged on trees; the most common 

 plan is the alternate ; ^^ in this only one leaf occurs 

 at a joint or node on the stem. The next in frequency is 

 the opposite, ^ fa where two leaves opposite each other 

 are found at nW the node. A very rare arrangement 

 among trees, though common in other plants, is the 

 whorled, tyA where more than two leaves, regularly ar- 

 ranged Wffi around the stem, are found at the node. 

 When a number of leaves are bundled together, a plan 

 not rare among evergreens, they are said to be fascicu- 

 lated or in fascicles. ^^^^^^ The term scattered is used 

 where alternate leaves are crowded on the stem. This 

 plan is also common among evergreens. 



CAUTION. In some plants the leaves on the side 

 shoots or spurs of a twig are so close together, the inter- 

 nodes being so short, that at first sight 

 they seem opposite. In such cases, 

 the leaf-scars of the preceding years, 

 or the arrangement of the branches, 

 is a better test 

 of the true ar- 

 rangement of 

 the leaves. The 

 Fig. 5. twig of Birch 



shown in Fig. 5 has alternate leaves. 

 There is one variety of alterna- 

 tion, called two-ranked, which is 

 quite characteristic of certain trees > 

 that is, the leaves are so flattened 

 out as to be in one plane on the 

 opposite sides of the twig (Fig. 6). 

 The Elm-trees form good examples Fig. e. 



