16 LIFE OF A TREE. 
Ordinarily, however, the imbedding in the soil 
is necessary for the growth of the seed, although 
it is by no means essential, since many seeds, if 
merely moistened with a little water, and kept 
in the dark, and in a room of moderate warmth, 
will begin to sprout. But they rapidly die if 
kept out of the earth for any length of time after 
this process has once begun. Probably every 
one has heard of the sailor’s mustard-and-cress 
apparatus. Those who have not may be in- 
formed that it is simply a worsted stocking and 
a bottle: the seeds are scattered inside the stock- 
ing, which is kept extended on the bottle and 
constantly wetted; and in a few days a dish of 
salad is produced by this odd miniature garden! 
And a little modification of this idea will enable 
the reader to follow us in our description of what 
next takes place. Let him construct the follow- 
ing simple contrivance :—procuring a piece of 
perforated zinc with fine holes, and cutting it 
into a triangular form, let each corner of the 
triangle be stuck into a flat piece of cork; place 
this in a tumbler of water, and it will float on its 
surface at the same time that the zinc is kept 
constantly half-covered with water. Now sprin- 
