THE PRINCIPLE OF COHESION. 



65 



position the tracheae of each pair of cords face each other. 

 At this point, then, they have quite lost their strictly axial 

 character of facing the centre, and the axis is therefore no 

 longer concerned in the structure. A little higher the 

 cayities of the ovaries (indicated by the dotted lines) appear 

 between the dorsal cord and the pair of marginal ones ; and 

 now the latter turn their spirals completely towards the 

 ovary cells, having rotated through 90° in all. The object of 

 this rotation is to enable them to send off cords to the ovules. 

 The second method is well seen in Geraniitm, Pelwrgonium 

 zonale, and Impatiens. A section of the receptacle of the 

 first two, made between the insertion of the stamens and the 

 pistil, shows five groups of three cords each, airanged as in 

 Fig. 13, a. Small portions of the ten staminal cords are 



SD 



Fig. 13,— Pelargonium : sections at baae of ovary (a, b, after Van Tiegbem). 



seen on the circumference of the section. The outermost 

 one of each group of three will form the dorsal cord of the 

 carpel. The two inner hare their vessels already turned 



