422 BOTANICAL GAZETTE [JUNE 
much impressed by the abrasive power of objects beaten about 
by the wind in winter in the case of firm paper tags attached by 
strings two inches long to twigs of apricot. During the winter 
they succeeded not only in marring the bark, but also in completely 
disintegrating all the buds within reach by simple contact while 
being blown about. It would seem that the beating together of. 
larger and harder objects like the branches themsclves would do 
even more damage. Therefore, in this casc also a firm outer coat 
is demanded. 
I believe that we are justified in concluding from these consid- 
erations that mechanical protection is one of the most important 
functions of the bud-scales—indeed the most important of all. 
Some other suggested functions of bud-scales. 
Gruss? included the storing of food material as one of the func- 
tions of bud-scales. Bud-scales undoubtedly do store considerable 
- @ . . 1 
food in some cases, but this is a secondary rather than a primary | 
function. We can scarcely consider this as having been an impor- 
tant factor in the evolution of the scales. 
GRooM®S suggests injury from excess of light as one of the things 
from which bud-scales protect the delicate young tissue; that 
when about to unfold the cell walls are thin and the chlorophyll 
is dilute and easily decomposed. If we conclude that the red color 
in young plants is for the purpose of modifying the light, then per- 
haps there is some danger to the young tissues of the bud from too 
strong light, since these usually become red. No direct evidence 
however is at hand to warrant this conclusion, and since such pro- 
tection could be obtained with the expenditure of less energy by 
the use of hairs or bloom, there seems to be little reason for con- 
sidering this a determining function of the bud-scales. 
One of the most interesting suggestions is that of Capura*® 
to the effect that in addition to protecting the delicate parts from 
loss of water, great radiation, cold, and too great gas interchange, 
34 Griiss, J., Beitrage zur Biologie der Knospen. Jahrb. Wiss. Bot. 23: 648. 189?- 
35 Groom, P., Bud protection in dicotyledons. Trans. Linn. Soc. Il. 3:255- 1893- 
36 CapuRA, R., Physiol gische Anatomie der Knospendecken dicotyler Laubbaiume. 
Breslau, pp. 42. 1887. 
