494 



changes occasioned by tlie process of respiration in the organic matter, 

 especially the nitrogen-free extract. These losses and changes have 

 been previously studied by other investigators, and in addition to a 

 description of his ovra. experiments, the author briefly reviews the inves- 

 tigations by Xol^be,* ]\[iiller-Tliurgau, and others. 



Xobbe studietl the changes both in weight and in chemical com- 

 position under varying conditions of temperature, moisture, light, et<^. 

 Brietiy, his exi)eriments indicated that the controlling factors in deter- 

 mining the loss in weight by Iceeping were tirst of all heat (temi)era- 

 ture), and next the state of moisture of the air, lieat increasing and 

 moisture rather diminishing it, and that light had no iierceptible eftect 

 on the loss in weight. .Measurements of the water and eaibonic acid 

 given off indicated the former to be from three to four times that of the 

 latter. The amount of carbonic acid given off seemed to be quite con- 

 stant, but the transpiration of water increased in March to nearly 

 twice the former amount. The per cent of starch increased in every 

 instance where the tubers were kept at a high temperature (25° to 35° 

 C). The starch content slightly decreased where the tuber.^ were kept 

 moist and cold, and remaineil practically unchanged when kept dry and 

 cold. 



Jfobbe's experiments were made entirely under artifical conditions, 

 and his obs<'rvations were conliiied to a small number of tubers. The 

 ]»iesent studies were on a much larger scale than those by Xobbe, 

 and were confined to the changes in weight and certain outward appear- 

 ances of the tubers. Of each o£ 11* different varieties of potatoes, KM) 

 tubers were selected at the tinu- of digging (early in October), brushed, 

 weighed, and placed in lead cyliiulers in a moderately dark. dee]), dry 

 cellar, where the temperature ranged from (P to IPC. From October 

 to April the tubers were weighed on the 1st and l.")tli of ea<'h month; 

 after April 1 weights were taken oidy on the 1st of each month. The 

 data secured indicate that under the conditions of the experiment the 

 losses in weight were greatest directly after digging, and decri-ased 

 from then till the 1st of .March, when they commenced to increase. The 

 average percentage losses of the 1'2 varieties from month to month were 

 as follows: October 2.02 per cent, November 1.18, December 0.50, Janu- 

 ary O.r.O. February O.Sl. :\Iarch 0.41. April 0.r)0. 



In the case of each variety the loss in February was larger than in 

 the month preceding or following, being in many cases doubled. The 

 loss of weight during the colder i)eriod uj) to the 1st of May was much 

 lower than during the foHowing sumnu'r. The former loss aggregated 

 on an average 0.17 per cent of the original weight, and the latter (May 

 to October) 21.57 per cent. 



The difference noticed in the losses of the different varieties did not 

 seem to bear any fixed relation either to the size of the tubers or to the 



Laudw. Vers. Stat., 7 (X865), pp. 452-46J, 



