GERMINATION AND GROWTH 35 
favorable to germination are present. Before releasing, they should be 
well shaken under the mercury to free them from air bubbles, and if the 
coats are loose fitting so that they can be removed without injury to the 
parts inclosed in them, they should be slipped off in order to get rid of any 
imprisoned air they may contain. Additional moisture may be supplied, 
if necessary, by injecting, by means of a medicine dropper inserted under 
the mouth of the tube, a drop or two of water that has been previously 
boiled. Keep in a warm, even temperature, under conditions favorable 
to germination, and compare the behavior of the seeds with those placed 
in the different vessels in Exp. 26. 
If appliances for this experiment are lacking, a rough approximation 
can be made by using the seeds of aquatic plants, such as the lotus, water 
lily, and the so-called Chinese sacred bean, sold in the variety stores, 
which we know are capable of germinating in the limited amount of air 
contained in ordinary soil water. Place an equal number of such seeds, 
of about the same size and weight, on a bedding of common garden soil 
in two glass tumblers. Fill one vessel a little over half full of ordinary 
soil water and the other to the same height with 
water from which the air has been expelled by boil- 
ing. Pour over the liquid a film of sweet oil or castor 
oil, to prevent the access of air, leaving the surface of 
the water in the other vessel exposed. In which do 
the seeds come up most freely ? 
Some seeds, especially those rich in proteins, as 
peas and beans, will germinate in a vacuum, because 
oxygen is supplied for a time by the chemical decom- 
position of substances in their tissues which contain it, 
but when these are exhausted, respiration ceases and 
death ensues. 
EXPERIMENT 28. DorEs THE DEPTH AT WHICH SEEDS 
ARE PLANTED AFFECT THEIR GERMINATION ? — Plant a, 
number of peas or grains of corn at different depths 
in a wide-mouthed glass jar filled with moist sand, as 
shown in Fig. 47, the lowest ones at the bottom, the 
top ones barely covered. Try different kinds of seed 
and grain, — radish, squash, cotton, or wheat, — and 
watch them make their way to the surface. Do you 
notice any difference in this respect between large 
seed’and small ones? Between those with thick coty- : : 
ledons and thin ones? At what depth do you find, Pee Rie es 
from your recorded observations, that seed germinate 4 which to plant 
best ? seeds, 
