43 



vegetable. We can easily demonstrate the occurrence of 

 this breathing- process in germinating seeds if we allow 

 moistened seeds to germinate m 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 v;:ll be immediately extinguished. 

 Respiration which is inseparable from active growth is a 

 process of slow combustion, and is always accompanied 

 by a rise m temperature. This can best be seen w^hen a 

 large mass of seeds are germinating together as, for in- 

 stance, during the process of malting, when barley grams 

 m 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 w^ill 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. I might, however, micntion that whilst 

 most seeds 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 famnly (Cruciferae), care should be taken not to 

 over-water the seedlings as they are liable to damp)-oft^ " 

 owing to the attacks of a parasitic fungus, which will be 

 dealt with in a subsequent chapter, \\lien 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 v-hich may be quite healthy and 

 normal. 



