276 Tlie Carbohi/drad's of the Mangold Leaf 



starting at 6 a.m. on Augnst 26th and ending at 4 a.m. next morning 

 (August 27th, 1913). The seeds were sown for this crop on June ytii. 



Series II. Intermediate growth, September lOth-llth, 1912, when 

 leaf formation is relatively small and the sugars are being vigorously 

 stored in the root, which is growing rapidly. 



Series III. Final stage of growth, October llth-12th, 1912; growth 

 of root practically complete, roots lifted at end of October. 



Method of expressing the results. 



As the amount of water in the leaves and stems varies widely W'ith 

 the meteorological conditions, the method of analysis described above 

 was decided upon, so that the results could be calculated upon the 

 total vacuum dried matter of the material dealt with. From the data 

 obtained it is possible also to calculate the relationship between the 

 material soluble in alcohol and that left undissolved and also the ratio 

 existing between the sugars at the diflerent times of picking. 



A. The Sugars of the Mangold Leaf. 



Series I. Early Growth, August 26th-27th, 1913. 



The results obtained in (ho first series of pickings (August 26th-27th, 

 1913) are given in Table I, and arc shown graphically in Fig. 4. 



Maltose and Starch are entirely absent from the mangold leaf through- 

 out the day and night. This is true also of the later stages of growth^ 

 (see Tables II and III). 



' We have found that altlioufjh very younf; seedlings of the mangold store starch 

 abundantly in the leaf, the stareli disappears entirely as soon as the root begins to grow 

 and becomes callable of storing the sugars elaborated in the leaf. It would therefore 

 appear that the mangold has the power of forming starch but never exercises it in the 

 later stages of growth when the sugars formed in the leaf can readily be translocated 

 away. The leaves of very j'oung plants appear, when examined by the chloral-hydrate- 

 iodine method, to be gorged with starcli after a bright day, probably owing to the fact 

 tliat the formation of starch at this stage is of service in preventing too high a concentration 

 of the sugars in the leaf cells whicli cannot be dealt with by otlier methods, but after about 

 the end of July, as our analyses and microscopic tests have shown, starch is invariably 

 absent because the sugar can then be translocated to the root and prevented from 

 accumulating. These facts throw a clear light on the function of the formation of starch 

 in tlie leaf, which clearly serves to reduce the concentration of tlie sugars and tlius prevent 

 it from attaining too high a value, such as would be prejudicial to the plant. In this connec- 

 tion the fact established in 1885 Ijy A. Meyer is of importance, vi/,. that plants wliich store 

 starch abmidantly contain comparatively little of the reducing or non-reducing sugars, 

 whilst leaves of plants like Trix germniiica. Allium cepa and snowdrop, which form very 



