244* Existence of electric Currents 



or in aai organ constituted for the purpose, to which the 

 term albumen * is generally applied ; not from its contain- 

 ing albuminous matter (chemically speaking), but from its 

 performing for the vegetable embryo an office analogous to 

 that supposed to be performed by the albumen, or white, to 

 the chick in the egg; viz. that of affording a supply of 

 nourishment, until its vital powers are sufficiently developed 

 to enable it to seek food for itself. 



The existence of this reservoir of starch may be very ele- 

 gantly shown by dividing longitudinally a seed of any of the 

 grasses (of wheat, for example), and dipping it into an aqueous 

 solution of iodine ; when it will be found that the albumen 

 will assume a fine blue colour, from the action of the iodine on 

 the starch it contains ; whilst the embryo will be merely tinged 

 yellow ; showing, in a very satisfactory manner, the division of 

 the seed into embryo and albumen. If, on the other hand, 

 we examine in a similar manner an exalbuminous seed, as 

 that of the horsechestnut (iE'sculus Hippocastanum), or of the 

 garden bean (Phaseolus vulgaris), nearly the whole of the 

 divided surfaces will assume a blue tint, in consequence of the 

 cotyledons of the embryo containing the reservoir of starch, in 

 the absence of a distinct and separate organ for the purpose. 

 Amylaceous matter is well known to be not only an organic, but 

 an organised, substance, consisting of an investing membrane 

 or sac, including a transparent matter soluble in water. In this 

 state, it would be capable of affording but little nourishment 

 to the expanding embryo ; but, in consequence of its being 

 readily convertible into sugar (a soluble and nutritious sub- 

 stance), it is peculiarly fitted for the purpose. This change of 

 starch into sugar is capable of taking place apparently inde- 

 pendently of any vital action exerted by the embryo; for, under 

 the influence of that degree of heat and moisture required for 

 the developement of the latter (aided, I believe, by the che- 

 mical composition of the tissue containing it), we find the 

 vesicles of starch burst, and the substance previously contained 

 in the ruptured sacs becomes rapidly converted into saccharine 

 matter ; thus presenting a supply of nourishment under a form 

 readily capable of being absorbed and elaborated by the yet 

 delicate organisation of the infant plant. 



Let us see how far these physiological considerations will 

 enable us to explain the developement of electricity during 

 germination, in the interesting experiments of M. Pouillet. 

 First, then, we find starch disappear, and be replaced by sugar ; 

 this change being accompanied by an evolution of carbonic 



* Perisperm of many authors : surely a more appropriate term than 

 albumen. 



