168 Physiologie. 



to lead to the compiete disappearance of the starch throughout the 

 stem, while in most trees the xylem retains more or less starch 

 and in still others both xylem and phloem retain some starch through 

 the winter. 



2. A few trees have shown a considerable increase of fat in 

 the phloem and xylem in late autum or early winter; but there is 

 insufficient evidence for the. belief that starch is transformed into 

 fat. In most trees the increase of fat is not marked. 



3. The trees that contain considerable fat in winter are some 

 of them hardwoods and some of them soft-woods as Popuhis delioi- 

 des, Tilia americana and Juglans nigra in the present paper, the 

 first two being soft-woods and the last a hard-wood. The soft-wooded 

 Salix alba contains but little fat, but considerable starch in its stem 

 in winter. From these results and those of European authors, it 

 would hardly seem justified to name broad-leaf hard-woods generally 

 as starch trees, and the soft woods and gymnosperms generally as 

 fat trees, as proposed by Fischer. 



4. As claimed by Sablon, so the work in this paper seems to 

 indicate no great increase in the content of sugar in stems and 

 roots except in the spring as the buds unfold. 



5. In the root, the transformations do not keep pace with those 

 in the stem, and starch remains the year round, the greatest re- 

 duction occurring in the spring. The roots of all nine trees studied 

 in the present work showed much starch in both phloem and xylem 

 all through the winter. 



6. The transformations of the carbo-hydrates are largely depen- 

 dent on the season, though the immediate conditions of temperature 

 have some effect. Thus Russow and d'Arnamont found that 

 several species kept in a warm glass-house over winter lost their 

 starch at the usual time; and in ihe work reported in this paper, 

 roots of trees exposed to the severity of winter by removing their 

 covering of earth did not appreciably reduce their starch. On the 

 other hand it is know that a stem, without starch in winter, will 

 form starch in a few days after placing in a warm temperature; 

 and Russow reports several species of trees that retained consi- 

 derable starch in the stem through a mild winter, but lost much or 

 all of their starch in the next winter, which was severe. 



7. Fabricius reports that the older stem of Picea excelsa does 

 not transform its starch to so great an extent as the younger stems. 

 Several of the trees examined in the present work have shown the 

 same thing; and hence it is quite likely that it is a general phe- 

 nomenon. 



8. Sablon has pointed out that the maximum for total hydrate 

 reserves for deciduous leaved trees is at the fall of the leaf in 

 autumn, whereas the maximum is at the opening of buds in the 

 spring for persistent leaved trees. Moore. 



Spoehr, H. A., The relation between photosynthesis of 

 carbon dioxide and nitrate reduction. (Science. II. 34. 

 p. 63—64. Jul. 1911.) 



It was found that a perfectly sterile aqueous Solution of potas- 

 sium or calcium nitrate will keep in the dark, even at 95°, indefini- 

 tely without forming a trace of nitrate. If a small quantity of col- 

 loidal platinum is added a reduction of the nitrate soon sets in with 



