588 M. BIOT ON APPLYING CIRCULAR POLARIZATION TO THE 



formed is also found in it, the fermentation of which enfeebles the ro- 

 tation without changing it. There is nothing [in its polarizing action] 

 which indicates the existence of cane or grape sugar. 



The nature therefore of these two sugars which are contained in the 

 foliaceous parts of the plant become changed like that of gum, by tra- 

 versing the collars of the ears ; and they serve as materials to the young 

 grain, by which they are formed into dextrine, and the other products 

 which compose the perisperm. 



I have made analogous experiments upon the young shoots of wheat, 

 but guided by the preceding, I have taken them more in division, ap- 

 plying them separately to the various foliaceous organs which in the 

 rye I had studied as a whole. In these organs I found diversities of 

 composition, of which I had no suspicion. 



I commenced my experiments on the 1 9th of May, upon young shoots 

 of wheat in which the ears were not yet developed. Suspecting that 

 the composition of the leaves was different from that of the stem, and 

 that they were destined to nourish it after fecundation, in the same 

 manner as the leaves of trees nourish or form the new annual layer of 

 bark and alburnum, I carefully detached the cylindrical stalk from the 

 vaginating leaves Avhich surround it, and treated these two parts sepa- 

 rately by the processes which I have just described, viz. by water, alco- 

 hol and fermentation. 



The stems, like those of the rye, presented three carbonated sub- 

 stances, viz. grape sugar turning to the left, cane sugar turning to the 

 right, and a substance turnmg to the left which may be precipitated 

 by alcohol. The relative proportions of these three principles varied 

 considerably with the progress of vegetation. On the 20th of May their 

 mixture produced a resultant of rotation directed towards the right, 

 showing that cane sugar was predominant in it ; but on the 4th of 

 June, the ears having left the stems and flowered, the resultant of the 

 stems had passed to the left, and was afterwards constantly maintained 

 in that direction, evincing that the cane sugar had become relatively 

 less abundant. It will jjresently be shown that in the ears it had passed 

 in excess. 



The leaves furnished results very different from those of the stems ; 

 they contained indeed a mixture of grape and cane sugar and a sub- 

 stance precipitable by alcohol and soluble in water after that precipita- 

 tion but, contrary to the stems, the proportion of cane sugar consider- 

 ably exceeded that of grape sugar ; besides, the precipitable matter 

 havino' exerted a rotation to the right seemed to be dextrine, while in 

 the stems the precipitable substance had a rotation to the left, and ap- 

 peared by this character analogous to gum. 



The leaves preserve this state of composition as long as their vitality 

 continues, but when fecundation is effected they may be seen gradually 



