40 PRINCIPLES OF GARDENING. [CH. I. 



^ fifth of its weight of oxygen gas, and this is the pro- 

 portion most favourable to the germination of the 

 majority of fresh seeds. Indeed few seeds will ger- 

 minate when this proportion is much reduced. Ra- 

 dish seed refuses to do so when it amounts to no 

 more than one-fortieth part, and lettuce seeds require 

 in it at the least one-sixth, when it amounts to only 

 one-eighth, they refuse to germinate. This is a reason 

 why of all kitchen garden seeds the lettuce requires 

 the most shallow sowing. 



So far are plants at their first germination from 

 being benefited by the application of stimulants, as 

 is supposed by the advocates of those menstrua, that 

 if the air supplied to them during that process is 

 contaminated by stimulating vapours, such as that of 

 sulphuric aether, camphor, spirits of turpentine, or 

 ammonia, germination is always in some degree 

 retarded and injured. 



Old seeds are alone those which require the addi- 

 tional stimulus of more oxygen to enable them to ger- 

 minate, and this as just stated is most readily aff'orded 

 by moistening them with a solution of chlorine, which 

 slowly extracts the hydrogen from water, and sets at 

 liberty its oxygen \rithin the integuments of the seeds. 



How oxygen operates in aiding the seed to develope 

 the parts of the embryo plant we cannot even guess 

 — we only know that most seeds have more carbon 

 (pure charcoal) in their composition than other parts 



