GRASSES RESIST COLD AND HEAT. 
185 
earth, stones, &c. composing their sides, fall by their 
gravity and form small heaps in our roads. A second 
displacement of the same kind and of larger amount 
occurs during the drying winds of March, for, a vast 
deal of mould, &c. loosened by the frosts, was not so 
impending as to be precipitated in the thaws, but, 
when the dry blasts of this month arrive, the work 
is completed by the partial evaporation of the water 
holding the mould together, and the physical force 
exerted by the wind itself. These operations 
doubtlessly take place in natural elevations, pre¬ 
cipices, deposits of soil, &c. and tend to reduce the 
earth to a more even surface in conjunction with 
other natural causes of more obvious influence. 
When frosts and snow prevail, and we see in all 
directions the baneful effects they have wrought on 
vegetation generally, we cannot but admire the 
wonderful care Nature has shewn for the lives of 
herbivorous creatnres in endowing the various spe¬ 
cies of grass with unusual powers of resisting cold; 
I first had my attention particularly drawn to this 
fact by observing that in the winter of 1837—8, 
remarkable for its long duration of frost, some rye 
grass (lolium perenne) I had sown in the previous 
October, was very sparingly affected, and only at 
the tips of the leaves, while some groundsel which 
had sprung up amongst it, notorious as every 
one knows for surviving our winters was nearly 
everywhere destroyed. All herbivorous animals 
resident in climates liable to snow are instinctively 
aware that they have to dig beneath this covering 
in order to find their provender, indeed this family 
of plants not only survive the winter, but even grow 
and flourish,—the snow keeping back the heat esca- 
* ping from the earth under all circumstances, gives 
the whole advantage of this to the plants thus 
snugly concealed under their protecting coverlid, 
Y 
