CHAP. VI. FUNCTION OF REPRODUCTION. 285 



found that if the nearly ripe seed be sown immediately 

 it is gathered, it will vegetate more speedily than when 

 it has remained in the pericarp until the complete elabor- 

 ation of the juices has taken place. This fact seems to 

 account for the very rapid manner in which corn vege- 

 tates in moist and warm weather, after it has been cut 

 and whilst still in the sheaf, or even before it is reaped. 



(287-) Action of Heat. The degree of heat requisite 

 to produce germination is different for seeds of different 

 species ; but, within certain limits, an increased tem- 

 perature acts as a stimulus upon all of them, the larger 

 and drier seeds requiring a longer time for the effect 

 to be produced. 



(288.) Action of Light. The action of light, though 

 not fatal is decidedly noxious to the germination of 

 seeds ; and the cause why it is so is obvious. Seeds 

 require to be freed from their superfluous carbon, by 

 this combining with oxygen ; but light is the chief 

 stimulus which operates in the decomposition of carbonic 

 acid, and in the fixation of carbon in the green parts. 



(289-) Action of the Soil. After germination is 

 complete, most plants grow in some soil adapted to their 

 nature, which serves them as a support, and more es- 

 pecially regulates the right proportion of moisture re- 

 quisite for their roots. 



(290,) Vitality of the Embryo. Every part of the 

 perfected embryo appears to be equally endowed with 

 life ; for if any portion be cut off, the remainder con- 

 tinues to germinate for a time, and will often repro- 

 duce the organ which has been detached. Thus the 

 radicle may be repeatedly cut away whilst it is de- 

 veloping, and the plumule will nevertheless elongate ; 

 or the plumule may be cut away and the radicle will 

 develop. There is of course a limit to these mutila- 

 tions, beyond which the young plant cannot be made to 

 grow ; but whilst it is still germinating, the vital force 

 cannot be said to reside in any one part of the indivi- 

 dual rather than in another. 



(291.) Connection between Buds and Embryos We 



