164 



THE STRUCTURE OF FLOWERS. 



CHAPTER XVIII. 



IRRITATION OF THE POLLEN-TUBE — THE ORIGIN OF CONDUCTING 



TISSUES. 



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. — a, section of (epidermal) conducting tissue of Fumaria ; b, that of Rubus ; 

 c, section of ovary of Crucifer (after Capes.) 



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

 50, a, represents a section of the stjlar canal, the lining 

 epidermis having its cells charged with such matters, while 



* Ann. dcs Sci. Nat., vii., 1878, p. 209. 



