POSITIVE D&DOUBLEMENT. 



69 



is clue to various causes ; one of these is by division of 

 the petals at an early stage of their development ; if the 

 division takes place collaterally there will be an increase 



Fig. 88. — Fuchsia. Section of older flower showing serial and collateral 

 division of petals, s, sepals; p, petals. (After Goebel.) 



in number of the members of the whorl ; if it occurs 

 serially, i. e. in the antero-posterior plane, the number 

 of whorls will be increased (figs. 87 and 88). Goebel 



Fig. 89. — Nerium Oleander. Section of bud of flower showing- pleiotaxy 

 of corolla (= double flower), s, calyx. (After Goebel.) 



gives a diagram of a flower of Nerium Oleander in which 

 there were several whorls of petals, the rest of the 

 flower being quite normal (fig. 89). The division may 

 in some cases be congenital; and not at all perceptible 

 during the development. 



