622 THE PHYSIOLOGY OF SOWING SEEDS. 
plants, and the direct influence of light, depend 
the digestion and appropriation of the food sent 
up from the roots. When material is brought to 
the building it has to be adjusted and built ; 
without this, the other conditions are useless. 
And so clever an architect is nature, that when 
she has her own unrestrained course, multiply 
culms to whatever extent she may, she ever 
disposes of and arranges them, so that these 
great and primary functions can be fully dis- 
charged. But if man in his ignorance sows his 
seeds so thick, that this thorough aeration, and 
this full action of direct light, or sun shine, 
cannot take place, then the functions of the 
plants are deranged, the food is not fully digested, 
and imperfectly appropriated ; the plant becomes 
sickly, structure increases slowly, and nature’s 
plans are all checked, and but partially finished. 
Weeds have the same effect; they rob the grain 
plants of air and sunshine, and thereby propor- 
tionally impoverish them. 
On the physiology of growth, or vegetation, 
we have but one more subject to mention, and 
that is, wherever practicable, to encourage 
growth, by stirring as often as is advisable the 
soil around plants during the early stages of their 
