THE PHYSIOLOGY OF SOWING SEEDs. 611 
them within the soil—like all other subterranean 
buds—during their season of repose; and because 
in the warm climates where they are indigenous 
they cannot easily be cut off from a due temper- 
ature for their germination,—she checks it by 
keeping them dry in the soil. We, on the other 
hand, dig them up from the ground, because we 
fear, and properly, the effect of frost upon them ; 
but instead of keeping them dry, we heap them 
up wet in immense quantities on the ground, and 
cover them over there to keep them so, with soil, 
thereby furnishing them, if they do not rot, with 
one requisite condition for germination; while 
the masses themselves raise and keep up the 
temperature to supply them with another, so that 
germination has not only commenced, but pro- 
ceeded considerably, when we dig them up again 
for planting. Then calculating upon the extra- 
ordinary degree of vitality, with which nature has 
endowed the tubers, we pull off the sprits, cut up 
the potatoes, and endeavour to reduce that vitality 
to as low an ebb as possible before we plant them. 
Within certain limits plants correspond with 
animals, in being able to transmit a portion of 
their vigour and qualities to their offspring. If 
we wish to cultivate a healthy race, we must 
