164 The Living Plant 



to their death by external causes, chiefly connected with the 

 large size they attain. 



The manifestations of life, wherever we know them, are as- 

 sociated closely with constant changes of matter and energy, 

 especially with respiration. But there is a case in which all of 

 these processes seem suspended, for our most delicate methods of 

 research fail to demonstrate them, and that is in resting struc- 

 tures such as seeds, Resurrection plants, and some low animals. 

 Not only can dry seeds retain their vitality for a great many years, 

 but in that condition they can withstand without injury a tem- 

 perature above boiling point, or even two hundred degrees below 

 freezing point. The question is important whether the usual 

 changes are proceeding in these seeds, but too slowly to be meas- 

 ured, or whether all processes stop and the vitality is really sus- 

 pended. The truth is not as yet known, but it is to be noted that 

 there is no logical difficulty in supposing that all of the processes 

 may slow down to a stop without any derangement of machinery, 

 precisely as an engine is stopped for the night simply by with- 

 holding the steam, leaving it all ready to start once more in the 

 morning. 



When this chapter was finished down to this point, it was 

 handed like all of the others to a critic for judgment. And this 

 is in substance the comment with which it came back. "The 

 chapter is clear enough in its statements, and appears to cover 

 the subject, but somehow it leaves you with a very unsatisfied 

 feeling." This opinion I take for a very high compliment, since 

 it shows that my chapter reflects precisely the scientific situation 

 of the subject. 



