FUNCTION IN PLANT LIFE 31 



conductor, we have, although in a slightly different form, 

 the same electrical arrangement as shown in Fig. 22 ; 

 the membranous covering of the tongue of the seed sub- 

 stance providing the dielectric and the seed substance 

 itself the inner or second conducting surface. 



It is worthy of note that in the edible chestnut the 

 white, pithy, positively charged area is larger other 

 things being equal than in the horse-chestnut, and this 

 might account for the conducting layer, c, of the first 

 taking, as is the case, a higher negative charge than 

 obtains in the second. It may also explain the slightly 

 increased positive electrification of the seed substance of 

 the former. 



As regards what I have termed a " repair outfit," both 

 the horse and the edible chestnut exude upon their cut 

 surfaces what bears the appearance of a starchy secretion. 

 This dries, and not only checks further evaporation of 

 moisture from the seed substance, but to some extent 

 restores the lost insulation. In the potato the phenomenon 

 is particularly noticeable, and the film is very quickly 

 formed. With the chestnuts the process is slower, but is 

 a protective measure of the same order. It would be 

 interesting to see whether in this case division of the seed 

 prevents germination. 



Another matter to which I should like to call attention 

 is that when freshly cut, the seed substance of the ripe 

 horse-chestnut is cream-coloured, or rather white, with a 

 faint tinge of lemon-yellow. After exposure to light, and 

 as soon as the starchy film develops, the cut surfaces 

 become yellowish-brown, with a deeper tint of yellow 

 showing beneath. This is, no doubt, a matter of electro- 

 chemistry, and as such somewhat beyond my purview, but 

 the suggestion has occurred to me that it may be a measure 

 of protection against actinic rays, or changes conceivably 

 introduced by them. 



