28 ELECTRICAL STRUCTURE AND 



remarkable. At all stages of development of the horse- 

 chestnut the seed substance is solid, and fills the whole of 

 the space within the inner membrane b, as shown in 

 Fig. 22, but in the edible chestnut it is more suggestive 

 of a foetus in the womb. I have cut some pods (un- 

 fortunately not now available for reproduction) in which 

 the seed substance appeared in semicircular shape, and 

 offered a weird resemblance to the foetus at a very early 

 period of its growth. Apart from that, however, there are 

 other essential points of difference. Both in the horse- 

 chestnut and the edible variety the secretion is markedly 

 acid, but whereas in the first the seed substance holds very 

 little liquid, that of the second is so heavily charged with 

 it as to fill or almost fill the cavity i, when the pod, and 

 with it the seed, is divided. 



In the case of the horse-chestnut the cut surface of the 

 seed soon discolours and becomes a brownish-yellow ; that 

 of the edible chestnut remains white for a much longer 

 time, although the conducting layer c dries up almost 

 immediately. One is a seed, pure and simple ; the other 

 is both a seed and a food. 



As will be seen in Figs. 22 and 28, the construction 

 electrically is much the same in both seeds, but whereas 

 in the horse-chestnut the seed substance is closely adherent 

 to the inner membrane b throughout, only a small portion 

 of the seed substance of the edible chestnut, in the posterior 

 part of j, is in its adolescence adherent to it, and this 

 part, as in the horse-chestnut, penetrates or protrudes 

 through the inner membrane by means of a tongue-like 

 projection to the limit of the conducting layer, c, which is 

 thicker than in the horse-chestnut seed. It, however, does 

 not connect with g (Fig. 25), but is nearer the centre of the 

 seed (g being, in the photograph, rather high up on the 

 left). This tongue is enveloped by an insulating membrane, 

 by which it is separated from the layer c and the outer 



