chap, hi.] SOWING SEEDS. 
45 
from crevices in apparently bare rocks; while 
not even a blade of grass will grow among 
the moving sands of a desert. 
The reasons for the second and third points 
of covering the seeds, and yet not covering 
them too deeply, appear more obvious; and 
yet they also require a little explanation. 
The seeds are covered to keep them in dark¬ 
ness, and to retain round them a proper 
quantity of moisture ; not only to make them 
swell and begin to vegetate, but to enable 
the roots to perform their proper functions; 
since, if exposed to the air, they would be¬ 
come dry and withered, and lose the power 
of contracting and dilating, which is essen¬ 
tial to enable them to imbibe and digest 
their food. Burying the seeds too deeply is 
obviously injurious in impeding the progress 
of the young shoot to the light; and in 
placing it in an unnatural position. When 
a seed vegetates too far below the surface, a 
part of the stem of the plant must be buried; 
and this part not being intended to remain 
under-ground, is not protected from the 
dangers it is likely to meet with there. It 
is thus peculiarly liable to be assailed by 
