THEIR ARRANGEMENT. 



139 



that the arrangement is of the quineuncial (f) order. It is further 

 noticeable, that the smaller number of parallel secondary spirals, 2, 

 agrees with the numerator of the fraction in this the § arrangement ; 

 and that this number added to that of the parallel secondary spirals 

 which wind in the opposite direction, viz. 3, gives the denominator 

 of the fraction. This holds good throughout ; so that we have only 

 to count the number of parallel secondary spirals in the two direc- 

 tions, and assume the smaller number as the numerator, and the sum 



Vertical Projection 

 of the -| Arrange- 

 ment. 



Vertical Projection of the A- 

 Arrangement. 



of this and the larger number as the denominator, of the fraction 

 which expresses the angular divergence sought. For this we must 



FIG 209 A cone of the White Pine, on which the numbers are laid dawn, and the leading 

 higher secondary spirals are indicated : those with the common difference 8 aie marked by 

 dotted lines ascending to the right; two of the five that wind in the opposite direction are 

 also marked with dotted lines : the set with the common difference 3, in one direction, and 

 that with the common di erence 2, in the other, are very manifest ia the cone. 



