64 THE STRUCTURE OF FLOWERS. 



generally be regarded as axial ; if, on tlae other side, i.e. 

 nearest to the ovary-cell, and if transverse sections exhibit 

 intermediate positions, in which they are central or scattered 

 irregularly within the phloem, they are then marginal and 

 placentary. 



They may change their position from one side to the 

 other of the cord, as far as I have observed, in three different 

 ways. The whole cord may twist to the right or left, as in 

 Hellebore (Fig. 12) ; or, secondly, it may divide into two, 

 and each half turn towards an adjacent half of another cord 

 and unite with the latter, as in Pelargonium zonale (Fig. 13, h) ; 

 or, thirdly, the trachejB may traverse the jDhloem and so pass 

 out at the opposite side at a higher level, as in Ivy (Fig. 14,/, 

 p. 68). In any case, as soon as the tracheae are so placed as 

 to effect their object of nourishing the ovules, they may be 

 pronounced to be unquestionably and strictly carpellary. 



I will take Hellebore as illustrating the first case. Fig. 

 12 represents a section of the floral receptacle taken imme- 



I 



a b 



c 



Fig. 1 2.— Hellebore : sections at base of ovary. 



diately above the insertion of the innermost stamens. There 

 are nine cords* oriented as axial, three of which are beg-inninar 

 to curve outwards to form the dorsal cords of the three 

 carpels. Sections made a little higher show that the three 

 pairs of cords have spread out and revolved so as to bring 

 their spiral vessels into a radial direction (b, c). In this 



* The trachetc are indicated by black lines or dots, the phloem being 

 inclosed within tho thin lines. 



