418 BOTANICAL GAZETTE [JUNE 
the tissues, then when the sunlight fell upon the buds in the morn- 
ing the scales would prevent injury from too rapid thawing. To 
support this view he found that shoots of Picea Engelmanni deprived 
of scale-caps perished, while normal ones did not. Shoots of Betula 
alba projecting slightly beyond the sheath were overtaken by a 
slight frost. The portion beyond the sheath was killed while the 
protected portion was uninjured. At a temperature of —3° R. the 
portion of the shoot outside of the sheath in Larix and Pinus Cembra 
was completely killed. A horsechestnut tree at —5° R. had the 
portion of shoot projecting beyond the scales killed, the rest was 
uninjured. At —5° R. shoots of this species were killed, while at 
—4° R. they were all right. Buds of Acer platanoides still in the 
scales were killed at —4° R. Populus cannot stand a cold of —5° R. 
after breaking out of the buds. Shoots of birch not inclosed were 
killed at —5° R., but not at —4° R; those still in the bud-scales 
were uninjured at —5° R. 
I am unable to agree with Griiss that these cases of protection 
are due mainly to the modification of the temperature. During 
the spring of 1902 I removed the scales from a large number of oak 
buds, also from birch and from maple. This was done about the 
time that the buds were swelling rapidly; but no frosts occurred 
afterward until the leaves were quite far developed. Many of 
the oak buds so treated died, and the rest were retarded or deformed 
in various degrees. The appearance in all cases was that of drying 
out—as though the tissue had simply shriveled up from lack of water. 
The birch and maple showed the same effect though in a less degree. 
Any one seeing these experiments could scarcely believe otherwise 
than that the loss of water caused the injury. When the shoot is 
young the epidermal cells are but slightly cutinized, and are there- 
fore much more pervious to water vapor than after having become 
more mature. At this period also the cells have probably not yet 
reached their full osmotic activity, and are still unable to replace 
rapidly the lost water. It is not surprising, therefore, that shoots 
should be injured at this period. Even in tropical regions, young 
tissue is protected against transpiration by being folded within the 
leaves, or in other ways. Groom’? has brought this point out nicely 
3° Groom, P., Bud protection in dicotyledons. Trans. Linn. Soc. II. 3:255- 1893- 
(RR eee a 
