310 The C(irhohi/(I rates of the Maiifjohf Leaf 



Even in the typical saccharose-forming plant the sugar cane, M. rdlet 

 informs us (private communication), reducing sugars are invariably 

 present. In the early stages of growth (first 5 or 6 months) the cane 

 may contain 3 per cent, of saccharose and 3 per cent, of hexoses ; later 

 the proportion becomes 5 per cent, of saccharose and 2 per cent, of 

 hexoses, then 7 per cent, of saccharose and 1 per cent, of hexoses until 

 finally the cane contains 12, 13 or even 16 per cent, of saccharose and 

 only 0-6, 0-5, 0-2, or even 0-1 per cent, of reducing sugars'. The quantity 

 of hexoses in the cane differs in different parts, increasing as one passes 

 from the lower to the upper part of the stem. This, we consider, points 

 to a steady influx of reducing sugars from the upper parts, followed by 

 transformation and storage in the lower parts of the cane, whicli in 

 this plant fulfil the functions of the root in the sugar beet and mangold. 



Finally it will be well to emphasise the difference that exists between 

 our views and those recently expressed by Pellet [1913] and by Colin 

 [1914]. Pellet holds that saccharose, dextrose and laevulose are formed 

 simullaneously {tout a la fois) in the leaves and that all these sugars 

 pass into the root, which possesses the property of transforming the 

 hexoses into saccharose. Colin expresses practically the same view — • 

 "la racinc re^oive a la fois du saccharose qui s'emmagasine et du 

 reducteur qui est polymerise." We are quite at one with these workers 

 that saccharose, dextrose and laevulose are jwesent at the same time, 

 but we consider that the cane sugar is probably first formed alone in 

 the mesophyll of the leaf, that it is transformed into invert sugar by 

 invertase in the veins and niid-rilxs and finally more and more com- 

 pletely in its progress througli the sieve-tubes of the stalks. It enters 

 the root entireh- in the form of reducing sugars and is therein reconverted 

 into saccharose. Once in this form the sugar cannot escape, until it is 

 put under contribution at the commencement of the following season's 

 growth, for the building up of the new shoot. 



StrakoscVs views. Strakosch [1907] has put iorwanl the view, 

 based on micro-chemical tests, that in the mesophyll of the leaf only 

 one sugar is present, namely, dextrose ; laevulose is said first to occur 

 in the small veins of the leaf and saccharose is formed as a final product 

 in the veins and mid-ribs. It is in the form of saccharose that the sugar 

 travels to the roots. Strakosch employed Grafe's [1905] micro-chemical 

 test for laevulose, based on the use of methylphenylhydrazine ; whether 



' Pellet [1914, 1] .shows that tlie reducing sugars found in the molasses of cane sugar 

 manufaeture represent the nriirinal hexoses of the juiee and are not produced by inversion 

 during the manufacturing operation.s. 



