FUNCTION IN PLANT LIFE 15 



THE POTATO. 



The potato plant receives its supply of current direct 

 from the earth, but it is open to doubt whether such is the 

 case with the tubers to which it gives birth. They are 

 connected with the parent plant by a filament or filaments 

 not altogether unlike the umbilical cord of the human 

 through which or by means of which they are energised. 

 In the potato shown in Fig. 14 I can trace only two eyes 

 to which such filaments might have been attached (marked 

 a and b). They are negative terminals communicating 

 with the outer negative system, while c, d, and e are 

 terminals (positive) of the lines /, g, and h. It is only 

 when these slightly darker lines reach the jacket that we 

 find a live or prolific eye. The unprolific eyes, so called, 

 are those by which the tuber is attached by a filament or 

 filaments to the parent root. 



It has been seen that some fruits seek to protect 

 themselves when cut or injured, or rather that Nature has 

 made in that regard some provision for them. 



In this respect the potato is well endowed. Very 

 shortly after being cut it exudes a starchy substance which 

 dries rapidly, and forming a film over the cut surface, 

 restores in some measure, if not entirely, the impaired 

 insulation, as well as preventing loss, by evaporation, of the 

 fluid, without which it must become electrically dead. 

 This tuber will, in fact, keep longer and grow better after 

 being injured than any other member of the vegetable 

 world with which I am acquainted, other things being 

 equal. 



THE JERUSALEM ARTICHOKE. 



There are several points of difference between this tuber 

 (Figs. 16 and 17) and the potato. It is covered with root- 

 filaments, is distinctly bipolar as regards the ends, and does 



