The Starch Content of Autumn Leaves. 145 



the different dates was determined quantitatively * and was 

 found to be as follows: August 17, 10.91 per cent; September 

 15, 10.33 per cent; October 23, 11.47 per cent; and October 28, 

 10.79 per cent. The starch present was based on the dry weight 

 of the material. 



While there is no surprising variation in the starch content 

 of the leaves of Liquidamber styraciftua collected on the different 

 dates, the largest percentage was found in material procured 

 October 23, the leaves collected at that time containing a con- 

 spicuous amount of red coloring matter. From October 23 to 

 October 28 there was a reduction in the amount of starch present. 

 The material collected at the latter date was picked up from the 

 ground. An eft'ort was made to obtain it soon after falling and 

 containing as much green coloring matter as possible, though 

 all the specimens contained more or less of the red pigment. It 

 would seem from these results that so long as active assimilation 

 takes place the starch content of the leaves of this plant varies 

 but little. As autumn approaches and the red coloring matter 

 develops the starch increases but again decreases before the leaves 

 are dropped. 



It is interesting to note in this connection the work of 

 Overton f who found that anthocyanin could be developed by 

 cultivating plants in sugar solutions. In the same series of ex- 

 periments he showed that an increase of the red pigment in the 

 cell was accompanied by an increase in the sugar content. 

 Combes % made a quantitative determination of the sugars and 

 insoluble carbohydrates in the red autumn leaves of several 

 different plants and compared them with the same substances 

 in green leaves collected under similar conditions. He found some 

 sugars and insoluble carbohydrates present in the red and green 

 material of all specimens studied. In three out of five plants 



*The method followed in determining quantitatively the amount of starch was as follows: 

 The do' weight of the material was obtained by placing the leaves as soon as gathered, 

 in a drying oven at a temperature of 100 degrees to 110 degrees C. The chlorophyll and 

 ?«ugars present were removed by washing thoroughly in 60 per cent akohol. The starch, 

 or >ub=tances capable of reducing copper in Fehling's solution were hydrolizcd by boiling 

 the material in a wea'.; j^olution of hydrochloric acid. After neutralizing the acid with 

 sodium hydrate the solution was clarified w-ith lead acetate. The lead acetate was removed 

 by precipitating with sodium carbonate. A definite quantity of this solution was added 

 to Fehling's solution and the whole boiled for two minutes. From the amount of copper 

 reduced, the per cent of starch per dry weight of leaf material was calculated. 



tOverton, E. Bcobachtungen und Vcrsuche uber das auftreten von rothem Zellsaft bei 

 Pflanzen. Jahrb. f. Wissen. Bot. ii: 171. 1898. 



iCombes, R. Rapports entre les composes hydrocarbones et la formation de rantbocyane. 

 Ann. Sci. Nat. Bot., 9 ser. 9 (1909). No. 4-5, pp. 27S-303. 



