220 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



can be called a plant eventually dies unless as frequently 

 happens a pair of buds situate between the axis of the 

 plumule and each cotyledon develop and form a couple of 

 upright pea stems, thus forming a complete plant. Appar- 

 ently therefore when from natural causes, old age and 

 the like, the vitality of a seed is diminishing, the plumule 

 is the first to die, the radicles resisting for a longer period. 

 Hence the radicles of Peas appear to have a greater 

 vitality than the plumules, and this greater vitality is 

 necessitated by the more exposed position of the former. 



If Peas are covered with water and tightly corked the 

 radicles burst the seed coat and may elongate to twice 

 their original length when their growth stops owing to 

 the absence of oxygen from the putrescent water. Even 

 before the elongation of the radicle commences the supply 

 of oxygen contained in the limited amount of water with 

 which the seeds are covered is exhausted by the rapidly 

 developing Bacteria, etc., and since no fresh oxygen can 

 reach the seeds it is difficult at first to see whence the 

 supply of free oxygen necessary to permit of the growth 

 of the radicle is derived. It might be obtained from a 

 store of intramolecular oxygen stored up in the seed itself 

 which is used when germination begins. If however Peas 

 be placed in a vessel completely filled with well boiled 

 water from which all oxygen has been driven out, though 

 they swell as usual the radicle does not elongate and 

 burst the seed coat. The seeds therefore do not contain 

 any stored intramolecular oxygen which might be avail- 

 able for commencing the first stages of germination. 

 The seeds when placed in ordinary water absorb oxygen 

 and water together and it is by means of this oxygen 

 that the metabolism necessary for the elongation of the 

 radicle is able to take place, though at that time the water 

 surrounding the seed is devoid of free oxygen. 



