164. 



THE STRUCTURE OF FLOWERS. 



CHAPTER XVIII. 



IRRITATION OF THE POLLEX-TUBE — THE ORIGIN OF CONDUCTING 

 TISSDES. 



The first effect produced by the action of the germination 

 of the pollen-tube is the formation of the so-called conducting 

 tissue or layers of specialized cells which nourish the tube 

 in its downward growth. Like glandular nectaries, this 

 tissue consists of small merismatic-like cells, highly charged 

 with nutritive and saccharine substances. In some cases it 

 is a metamorphosed condition of the epidermis alone, as 



Fig. 50.- 



, eectioa of (epidermal) conducting tiiiRU'? of Fvmaria; b, tliat of Rubia; 

 c, eectioa of ovary of Crui-ifer (after Capes.) 



M. Capes has shown in his researches,* as in Fumaria. Fig. 

 60, a, represents a section of the stylar canal, the linin;^ 

 epidermis having its cells charged with such matters, while 



• .47171. des Sci. Nat, vii., 1878, p. 209. 



