1 hive apy age 
1906] WIEGAND—BUDS AND TWIGS IN WINTER 4II 
beneficial importance in preventing rapid changes, even if such 
changes are detrimental. 
Rapid thawing in itself is probably not detrimental to buds and 
bark. 
Bud-scales seem of no benefit in keeping out the heat from sudden 
bursts of sunshine. They do not appreciably prevent the loss of 
water by preventing alternate thawing and freezing. They do not 
retard radiation to any important degree. 
Dark-colored bud-scales indeed, instead of preventing tempera- 
ture changes actually seem to absorb more heat than if they were 
lighter colored. 
“Wool” in buds does not function by modifying temperature 
changes. 
Bud-scales do not seem to function in modifying temperature 
changes when the bud is opening. 
Bud-scales may protect the delicate tissues in the tropics from 
heat, but it would seem rather from excessive transpiration due 
to great heat than from the heat itself. 
Finally, we may conclude that as a factor in the evolution of 
buds and bark in cold climates temperature considerations have 
probably played a very minor part. 
Internal moisture. 
Of all the more important factors concerning the function of 
bud-scales, perhaps that relating to their inhibiting effect upon the 
loss of internal moisture is the least recognized by people in general. 
In scientific literature, however, it has received considerable atten- 
tion. Most authors now consider this one of the principal functions. 
of the bud-scales and also of the bark. The subject has been dis- 
cussed briefly by CapuRrA*3 and Groom,’* but also more fully by 
Gritiss,?5 who performed a number of experiments to demonstrate 
the point. His results may be summarized as follows. The first 
function of the scales consists in protecting the inner meristematic 
23 CaDURA, R., Physiologische Anatomie der Knospendecken dicotyler Laub- 
baume. Breslau. pp. 42. 1887. 
Pe Groom, P., Bud protection in dicotyledons. Trans. Linn. Soc. II. 3:255. 
25 Grtss, J., Beitrige zur Biologie der Knospen. Jahrb. Wiss. Bot. 23: 649. 1892. 
