LEAF ARRANGEMENT. 



103 



over the first. Frequently the leaves are 



whorled, as showu iu the 



galium or bed - straw 



in Fig. 79. In some 



whorls or circles there 



are ten or more leaves. 



Fascicled or clustered 



leaves are shown in 



the larch or tamarck, 



Fig. 80, and in the 



pitch pine in Fig. 81. 



In the pines the num- 

 ber of leaves in a cluster is a reliable aid in 



determining the species. In the white pine 

 the leaves are always 

 five in each fascicle, 

 in the scrub or Jer- 



Fig. 79. 



Fig. 80. 



rangement of 



sey pine two, and in 

 the pitch pine three. 

 The study of the ar- 

 leaves is known as 

 phyllotaxy, " leaf arrangement." It 

 has proved the existence of definite 

 order where order is least to be ex- 

 pected. It has discovered this order ^^s- 81. 

 in the disposition of leaves, and in the ar- 

 rangement of the parts of the flower, and 

 in many cases even in the arrangement of the 

 seeds in the pod. 



