360 
universal destruction of tliese trees. The Lombardy Poplar in this 
present year shows no sign of growth from the trunk, proving 
thereby, that the root has suffered more than the trunk. The only 
explanation of the facts observed which commends itself to me is, 
that Avhile in 1860 the effects of the frost were produced aerially, 
last winter the effects of the frost were produced by the penetration 
of cold into the ground, thus affecting the roots. 
“ In porous shallow soils where the roots lie near the surface, the 
trees are killed wholly or in part, but in the deeper soils escape to 
a greater extent. In the shallow soils, those trees which receive 
the sun’s rays at their roots, escape better than those in woods, or 
where the roots are sheltered, and this I think is the reasoii of the 
south side being the only part left alive. By roadsides, too, besides 
obtaining the sun’s warmth, the roots passing under the road are 
better protected. 
“Why is the Lombardy Poplar the only tree killed by last winter’s 
frost? This is a (question for which I find no satisfactoiy solution, 
unless it be that their remote progenitors, growing in a district 
where the soil is strongly heated in summer, and protected by sun 
or snow from deeply penetrating frost in winter, have transmitted 
to their offspring a peculiarity in the root fibrils which renders them 
intolerant of prolonged cold. Whether this be so or not, the fact 
of such wide-spread mortality in this species is certainly very 
remarkable, more especially as no other kind of Poplar has shown 
any sign of injury.” 
(4) W/iaf was the came that made last winter specialhj fatal f 
]\Ir. Marsham writes : “ My own impression of the cause why so 
many died last winter was not so much the actual cold, but from 
the variableness of our temperature in England ; freezing one day, 
thawing the next, and the tree not being very hardy was not in a 
quiescent state.” Mr. Marsham contrasts the winter in Switzerland 
(of 1858—59) with our English winter : “Erom what I remember 
the frost lasted continuously for many weeks I do not 
think it once thawed till the general break-up, and in a very short 
time the beautiful Swiss flora eovered the neighbouring mountains. 
It seemed as if we jumped at once from winter to summer : and 
this severe continuous frost did not injure Judas trees, wliich ismre 
killed in England in 1860 — 61.” 
