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 ina 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 alone 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, 2.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 
