PHYLLOTAXY. 



95 



fig^-jc) 



F,gMS3 



Fig.»<5a 



V 



F, 



g-^<?V. 



fiff.^Si, 



circuits of the stem, so that its exponent 

 will be two-fifths. If the second leaf were 

 No. 9 the appropriate fraction would be 

 three-eighths, the cycle making three 

 turns and containing eight leaves (Fig. 

 484). It will thus be observed that these 

 fractions form a series, in which each 

 possesses a numerator equal to the sum 

 of the numerators of the two preceding 

 and a denominator equal to the sum of 

 the denominators of the two preceding. 

 No cycles occur among the higher plants 

 with which we are concerned, which can 

 be indicated by tiny fraction not thus 



formed. 



Noticing these fractions still further, 

 we observe that the denominators will in- 

 dicate the number of orthostachies upon 

 the stems which they represent, and that 

 the value of the fraction will represent 

 the divergence of, or part of a circle be- 

 tween, any two leaves adjacent in the 



