ve SE <a 
1906] WIEGAND—BUDS AND TWIGS IN WINTER 417 
be taken in the same place under the same weather conditions. 
The rise of 5 per cent. is only a small part of the whole water lost. 
How much will rise into the bud when the tissues remain thawed 
was not determined. 
The question arises whether the damage to the bud is done 
while the latter is frozen or thawed. I believe that injury is done 
both while thawed and while frozen, for the reason that the loss 
of water from unprotected buds is sufficiently great to cause death 
at either time. However, probably more damage is done above 
freezing point, because here the loss must increase with the tem- 
perature much faster than does the conduction of water in the bud. 
The evidence therefore seems to be sufficient to warrant the 
conclusion that the loss of water during the winter is a danger against 
which the bud-scales and bark serve as protective organs. Next 
to the warding off of mechanical injury this is probably their most 
important function. 
Protection oj the young shoot. 
In many trees, notably in maples, horsechestnuts, oaks, etc., 
the growth of the young shoot is accompanied by a growth in length 
of the bud-scales, especially of the inner ones, so that a sort of 
telescopic tube is formed in which the young shoot remains concealed, 
frequently until a growth of 2—8°™ has taken place. The function 
performed by the bud-scales at this time has long been a subject of 
interest to investigators, among whom Gruss’? has given us the most 
comprehensive account. 
According to Griiss, the protection lies in the ability of the 
Scales to prevent the penetration of extreme cold on freezing, or 
great heat when thawing out. The greatest danger to buds from 
cold, he says, is in the spring after activity has commenced, when 
a few degrees of frost will often kill the tissue. It is on just such 
occasions that the frost is likely to be of short duration, and to occur 
for a few hours only, just before sunrise. It is quite conceivable 
that the non-conductivity of the scales would be sufficiently great 
to prevent an extreme fall of temperature within the bud during that 
short time. Again, if the cold was severe enough actually to freeze 
0 Gruss, J., Beitrage zur Biologie der Knospen. Jahrb. Wiss. Bot. 23: 649. 
1892. See also HENSLOW, I. c. 
