Wilcox — Winter Condition of the Reserve Food, etc. 69 



Art. YII. — The Winter Condition of the Reserve Food 

 Substances in the Stems of certain Deciduous Trees ; by 

 E. Mead Wilcox. 



The investigations, of which this is a preliminary account, 

 were undertaken to determine more definitely some of the 

 essential physiological processes involved in the dormant 

 periods of our woody plants. Stated briefly the problem was 

 (a) to determine what are the conditions in which the reserve 

 food substances are stored in the twigs during these dormant 

 periods, i. e. during the winter, and (b) what if any changes 

 they undergo during this period, and (c) how do these changes 

 affect the renewal of activity by the buds at the beginning of 

 the subsequent season of growth. 



And it is to be noticed that the phenomenon of the renewal 

 of activity by buds is not essentially unlike the process of the 

 germination of seeds — in fact both phenomena may well be 

 classed under the one head of the germination of dormant 

 organs. 



It is well known that this periodic alternation in the vegeta- 

 tive growth of the tree of a period of growth and a period of 

 rest is so regulated that both normally occur at definite seasons 

 of the year. And this fact has led many writers to ascribe 

 this periodicity to the effects of temperature and in general to 

 external rather than to internal changes. However, these 

 dormant periods often occur under the most favorable condi- 

 tions both as to moisture and temperature, while germination and 

 the renewal of vegetative activity quite as often occur under 

 rather adverse external conditions. In fact more careful study 

 tends to show that the apparently close dependence existing 

 between vegetative rest and unfavorable external conditions is 

 due to the fact that in the cells there are taking place certain 

 remarkable changes that require for their completion a dormant 

 period. This fact was definitely determined for the potato 

 tuber by Miiller-Thurgau '82, '85. 



The two very interesting papers by Miiller-Thurgau 

 give the chemical changes that occur in the potato during 

 its dormant period. In fact his work shows certainly a 

 dependence of the renewed growth of the tuber upon 

 the completion of these changes in the starch and other 

 reserve food material stored within the tuber. Hartig, '58, 

 expressed the view that the starch is stored in the cells of the 

 bark and wood during the summer and that it remains there 

 unaltered in position or amount till it is entirely or partially 

 consumed in the production of new organs the following 



