43 
vegetable. We can easily demonstrate the occurrence of 
this breathing process in germinating seeds if we allow 
moistened seeds to germinate in a closed jar. The latter 
‘will soon. lose all the oxygen it previously contained, and 
carbonic acid will be found to have taken its place, as can 
easily be seen by the fact that if a lighted taper is intro- 
duced into the jar it will be immediately extinguished. 
‘Respiration which is inseparable from active growth is a 
process of slow combustion, and is always accompanied 
by a rise in temperature. This can best be seen when a 
large mass of seeds are germinating together as, for in- 
stance, during the process of malting, when barley grains 
in large heaps are passing through the early phases of ger- 
mination, the starch they contain in the resting stage being 
transformed into the sugar known as maltose. By plung- 
ing the hand into a heap of barley which is undergoing 
this change one can readily detect the heat which is being 
evolved. The active need for oxygen by germinating 
seeds will make us careful to keep our seed beds porous 
and to prevent the soil above seeds from becoming caked 
and therefore impervious to air. 
Details of the various methods of germination will be 
found in most botanical textbooks and need not be dealt 
with in this lecture. J might, however, mention that whilst 
most sceds germinate best in the absence of light, there are 
some small seeds which should be sown superficially, as 
light seems to be beneficial to their development. This is 
particularly the case with the seeds of some grasses. An 
important point in sowing seeds, apart from taking care to 
give them the proper depth, is to ensure that the soil with 
which they are covered is fine and friable, so that the 
seedlings have no difficulty in forcing their way up to the 
light. In the case of mustard, cress and other members of 
the same family (Cruciferae), care should be taken not to 
over-water the seedlings as they are liable to “ damp-off ” 
owing to the attacks of a parasitic fungus, which will be 
dealt with in a subsequent chapter. When dealing with 
some seeds which germinate irregularly, possibly owing to 
their age or on account of their having been stored during 
the winter when they should have been sown immediately 
after maturing, it may be advisable to keep the seedpan 
going for a considerable time as a succession of seedlings 
may be produced, all of which may be quite healthy and 
normal. 
