32 GARDENING FOR ALL. 
The essential conditions of germination are heat, water, 
air and darkness. In the absence of any of these essentials 
there can be little or no growth. Water is necessary for the 
solution of the nutritive matter of the seed and for exciting 
the endosmatic—or inward drawing of moisture—action of 
the cells. No circulation or movement of fluids in the seed 
can take place until water is taken up. Seeds imbibe a large 
quantity of water, and in so doing their cells become 
distended, by which means they are enabled to burst the hard 
coverings which often surround them. Wet boots may be 
kept in shape and dried by filling them with oats as soon as 
removed from the feet ; having answered their purpose the 
oats may be dried and used again when required. 
The amount of heat required varies very much, but 
generally the plants we cultivate in Great Britain, under 
glass and out of doors, will require warmth varying from 45° 
to 70° mean temperature, according to their native habitat. 
Heat is evolved in the process of germination. When the 
seed is of good quality, containing abundance of starch, this, 
when the seed swells, is converted into sugary matter for its 
nourishment; but if the seed is imperfect and contains gum 
in the place of starch, the gum is converted into vinegar and 
the seed decays. 
Air is necessary for the purposes of germination, and the 
presence of Oxygen gas is required in order to aid in the 
changes which take place intheseed. When seeds are buried 
too deeply in the soil and deprived of air, they do not grow ; 
but if they are brought sufficiently near the surface of the soil 
at some subsequent period, germination often takes place and 
strange plants make their appearance. 
Seeds germinate more freely in darkness than in light : 
therefore, when small seeds like those of calceolarias, begonias, 
and lobelias are sown on the surface of the soil, some material 
such as paper, must be placed over them to intercept the rays 
of light. 
