294 REPORT OF THE BOTANICAL DEPARTMENT OF THE 
Some rather suggestive results along that line were obtained 
by R. A. Emerson’ from an experiment designed to indicate 
the relation of different percentages of soil moisture and 
mulching to winter-injury of roots. One-year-old apple and 
two-year-old cherry seedlings were planted in boxes of loam 
soil of various degrees of moisture. Some of the boxes were 
put out on open ground and one into a cool, dry cave. In 
the open some boxes were mulched and others left exposed. 
The experiment was begun in December and ended in February. 
None of the cherry roots seemed injured severely enough to 
prevent further growth, while many of the apple roots were 
much damaged. The dead, brown cortical regions from the 
surface of the ground down one to seven inches, observed on a 
number of these trees, have a suggestive resemblance to Crown- 
rot. It seems that similar injuries were found on other young 
trees which were not in the experiment. The tops of these 
root-injured trees were generally unaffected. The apple seed- 
lings in unmulched soil with 10.4 per ct. soil moisture were 
injured decidedly more than those in boxes with 25.6 per ct. 
of moisture content. Straw mulch seemed to lessen liability to 
frost-injury due to low moisture content of the soils “ Just 
why severe freezing should injure roots worse in rather dry 
than in moist soil is not shown by the test reported above. On 
further investigation it may be found that roots are simply 
unable to withstand severe freezing or to recover from it 
unless surrounded by an abundance of moisture. Be this as it 
may, it is quite probable that one cause of the great injury 
in rather dry soil is alternate freezing and thawing.” Emer- 
son thinks that piece-root grafting of hardy varieties (making 
own-rooted trees) is advisable and also that budded trees 
should be planted deep, Cultivation and cover-crops are rec- 
ommended. 
More recently, he published® some observations on the rela- 
tion of a tree’s wood-maturity and its resistance to cold. It 
™ Experiments in orchard culture. Nebr. Agrl. Expt. Sta. Bul. 79, pp. 
26-32. 1903. 
* Nineteenth Ann. Rpt. Nebr. Agr]. Expt. Stat., pp. 101-10. 1906. 
