1899] TREES IN WINTER 403 



the leaf falls, easily degrades and suffers what may be called a dextrine 

 change. 



Is the process of deassimilation likewise checked and brought to 

 rest within the inner arcanum of our trees in winter ? Do 

 tannoids, resins, volatile oils, waxes, tannins, and coloured pigments 

 continue to be produced as the outcome of the spent and exhausted 

 energy of the chlorophyllian protoplasm ? " Assimilation," says 

 Mesnard, " may be very feeble and even be annulled completely, but 

 deassimilation should not be null as it is indispensable to the proper 

 functioning of the cell." Wigand, in a general way, declared that the 

 young shoot in the condition of winter-bud contains no tannin, but has 

 starch ; he imagined that the tannin is changed into starch, and in 

 that condition held as it were its winter sleep. In 1875 Oser con- 

 cluded that the tannin of the current year's twigs of oak decreased in 

 winter, it being possibly used up in a kind of internal respiration, the 

 tannic acids being very easily oxidisable. In 1888 E. Schulze dis- 

 cussed the question, Are the leaves of evergreen trees emptied in 

 autumn like caducous leaves, or are they filled with reserve materials 

 like the other persistent organs ? He performed numerous micro- 

 chemical experiments, and concluded that only in Gymnosperms and 

 in most Dicotyledons do the leaves serve as magazines of reserves 

 during the resting period. He found that not only starch but fatty 

 oil and tannin may still be detected in the winter foliage ; sometimes 

 tannin is found there alone, sometimes it exists along with starch or 

 oil, but they are rarely found side by side in the same cell ; moreover, 

 when oil accompanies tannin, the cells which contain the oil are 

 generally deprived of starch. Starch and tannin occur in the winter 

 leaves of oak, holly, mistletoe, spindle-tree, etc., whereas those of ivy, 

 guelder rose, firs, pines, etc., contain tannin only. G. Kraus carefully 

 examined the youngest shoots of several trees and shrubs monthly 

 during the winter, and found that the tannin of the twigs formed in 

 the preceding vegetation period undergoes no change in the winter 

 months, and hence Oser's idea of its mission as a respiratory material 

 falls to the ground, and Schulze's and Haberland's opinion that it is a 

 reserve substance is consequently unsatisfactory. 



Nevertheless, I think there is some satisfactory evidence to prove 

 that if tannin, i.e. the capital product of deassimilation, does not increase 

 during the dead months of December, January, and February, it at all 

 events develops to some extent ; this is to say, by further exposure to 

 the oxidising agencies of light and air it suffers dehydration, or a 

 molecular rearrangement of its constituent atoms. For instance, it is 

 during the wintry gloom that the leaves of ivy assume their brightest 

 red, the buds of the Norway maple are red in autumn but become of a 

 still darker red in the course of the winter, the holly berry never 

 shows so ruddy a radiance as about the merry Christmas time, and 

 many other illustrations may readily be recalled. Indeed, from the 



