THE LEAF. 



45 



Plan A. Leaves of Sedges (Carex, Sci?-pus), Tulip, Alder, Birch, &c. 

 Plan f. Leaves of Apple, Cherry, Poplar, Oak, Walnut, &c. 

 Plan f . Leaves of Flax, Plantain (Plantayo) (fig. 50), Holly, Aconite, c. 

 Plan jV Eyes (buds) of Potato-tubers, cones of Pinus Sirobus (fig. 51). 

 Plan ^j. Cones of Spruce-fir (Abies excelsa). 



When the leaves are very numerous and much crowded, it is often 

 difficult to trace the fundamental spiral, as the vertical ranks are not 



Fig. 51. 



26 



27 



24 



oo 



23 



20 



18 



13 



1(3 



11 



14 



15 



12 



10 



Cones of Pinus Sirobus, with the scales in the J>_ arrangement. 



evident. In these cases the arrangement is ascertained by studying the 

 secondary spirals which appear. These are more or less numerous, ac- 

 cording as the fractional expression of the fundamental spiral is higher. 



For example, in examining the cone of the White Pine, a complex 

 spira arrangement is at once recognized, which will be understood by 



