THEIB ARRANGEMENT. 



139 



that the arrangement is of the quincuncial (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 f arrangement ; 

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

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

 of the fraction. Tliis 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 numeratoi", and the sum 



Vertical Projection Vertical Projection of the Jr 



of the ^ Arrange- Arrdngement. 



ment. 27 



26 



25 

 21 



23 

 22 

 21 



20 

 19 



25 



21 



23 



19 



IT 



16 



18 



15 



13 



10 



18 



17 



15 



15 



14 



13 



12 



10 



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 down, and the leading 

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

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

 also marked with dotted- lin^^ : the set with the common difference 3, in one direction, and 

 that with the conunon difference Sj in the other, are very maaife&t in the cone. 



