38 



Science of Plant Life 



In the alternate arrangement each node bears one leaf. 

 This is also spoken of as the spiral arrangement, because a 

 line drawn through successive leaf bases 

 forms a spiral about the stem. Some- 

 times, as in the corn plant, the spiral 

 passes half around the stem in going from 

 one node to the next (page 50). In other 

 plants, like the sedges, the spiral passes 

 but a third around the stem between 

 nodes. In several of our common fruit 

 trees, as the apple and the peach, the 

 spiral between nodes passes two fifths 

 around the stem. These variations of 

 the spiral arrangement are called the two- 

 ranked (Fig. 28), three-ranked (Fig. 23), 

 and five-ranked 

 arrangements. 



Fig. .3. Asedge(Z)«7/- In the Opposite 

 chium), showing three- arrangement two 



ranked arrangement of j^^^^g ^^^^^ ^^ 

 the leaves. 



each node. The 

 leaves at successive nodes, how- 

 ever, are at right angles to each 

 other (Fig. 25), giving four ranks 

 of leaves. The maple, ash, dog- 

 wood, and lilac furnish examples 

 of the opposite arrangement. In 

 the whorled arrangement the 

 leaves are in a circle about the 

 node. The Indian cucumber root 



{Medeola) and the 



Fig. 24. Indian cucumber root, 

 showing the whorled arrangement 

 wood lily of the leaves. 



