Variation in the Food Reserves of Trees. 233 



them lost all, or nearly all, their starch, notwithstanding the 

 warmer temperature of the house, Russow concluded that the 

 solution of the starch is independent of immediate climatic con- 

 ditions. Russow's view was that the starch was transformed 

 into fat. 



In a report to the Versammlung russicher Naturforscher und 

 Aerzte, Odessa, Grebnitzky and Baranetzky^ stated that their 

 examination showed that the autumn starch disappeared wholly 

 from the phloem of the stems of trees in winter, and disappeared 

 wholly from the xylem of the stems of soft-wood trees, while the 

 xylem of hard woods showed merely a reduction in the amount of 

 starch. They, too, supposed that the starch was transformed into 

 fatty oil. 



In the year 1891, following a shorter paper on the same subject, 

 Fischer^ published a very extensive and detailed account of his 

 studies of the reserves of trees. He confirmed the reports of 

 former observers as to the disappearance or reduction of starch 

 in the stems of trees as the season advanced from autumn to 

 winter, and summed up the whole annual transformation of the 

 non-nitrogenous stored material as follows : At the time of the 

 fall of the leaves in autumn, the stems of trees show a starch 

 maximum ; in winter there is a starch minimum, and in early 

 spring a regeneration of starch, producing a second starch maxi- 

 mum, followed later in spring by a second starch minimum. The 

 soft-wood trees in general dissolve all their starch in winter, re- 

 placing it in whole or in part with fat, while the hard-wood trees 

 in general retain a large amount of starch especially in the xylem 

 in winter, and show but little fat. This high percentage in winter 

 of starch on the one hand, or of fat on the other, allows trees to 

 be divided into two groups, starch-trees ( composed mostly of the 

 hard-woods), and fat-trees (composed mostly of the soft-wood 

 and conifers). The starch minimum of spring is followed by a 

 glucose maximum at the time of the unfolding of buds; but this 

 maximum soon diminishes as the sugar is consumed in the for- 

 mation of new tissue. Glucose may appear in some trees as a 

 product of starch solution in winter, but not to the extent that fat 



'Bot. Centrblt. XVIII, 1884, 157. 



^Beitrage zur Physiologic der Holzgewachse. Jahrb. wiss. Botan. XXII, 

 1891, 73- 



