1906] WIEGAND—BUDS AND TWIGS IN WINTER 305 
WINTER FUNCTION OF BUD SCALES. 
Bud scales are obviously for the purpose of protecting the tender 
inner shoot from detrimental external influences; but how is this 
protection accomplished? This is a subject regarding which 
opinion has varied widely and does still at the present time. I 
believe we shall find that the most widely accepted views, strangely 
enough, are not the correct ones, even though the subject appears 
so simple. We can conceive of such protection taking place along 
four lines: (1) by keeping out external moisture; (2) by preventing 
the penetration of cold or sudden changes of temperature; (3) 
by preventing the escape of internal moisture; (4) by warding off 
external mechanical injury. It seems best to discuss each of these 
in turn, and in this way determine the extent to which cach one 
is operative. 
External moisture. 
There is a widespread belief that bud-scales function by keeping 
out the wet. The subject, however, is a difficult one to determine 
experimentally, and I can find no reference in literature to such 
experiments having been performed. Let us first determine the 
possible ways in which water might be supposed to injure the embry- 
onic tissues. First, the cells might absorb too much water and 
thus become more sensitive to frost. It seems quite reasonable to 
believe that a cold spell following such an event might «nd the life of 
the bud completely. Again, through gradual absorption of the air 
by the water the latter might replace the air in the intercellular spaces, 
thus preventng free respiration. Or again, if a thawing bud were 
surrounded by water, the latter, instead of.air, would be drawn in to 
fill the vacant intercellular spaces, the final result being the same 
as in the last case. Lastly, one might expect that the freezing of free 
water between the embryonic foliar and floral parts might cause 
mechanical injury. 
purple buds and twigs of peach. Green twigs and especially whitened ones warm 
up less each day and this color would therefore be protective. I believe it may quite 
likely be true that delicate buds might suffer by such violent treatment either from 
stimulated activity or increased transpiration, even though hardy trees are apparently 
indifferent. Das Verhiltniss der Farbe zur Tétung von Pfirsichknospen durch 
Winterfrost. Inaug. Diss. Halle. 1902. 
