l68 PLANT RESPONSE 



I have obtained very perfect records even when the passing 

 traffic was at its thickest. How true this is may be seen 

 from the photographic record of a thermo-mechanical curve, 

 given in fig. 85. 



It will be noticed from the curve that, as the temperature 

 rose, there was a continuous preliminary elongation, which 

 was suddenly reversed by the exci- 

 tatory contraction at the death-point, 

 found in this case to be 59"6° C. 

 If desired, the photographic curve 

 itself may be made to indicate the 

 different temperatures at different 

 parts of the curve. This is secured 

 by interrupting the light for a time 

 at, say, every half degree of rise of 

 temperature. As in the anisotropic 

 death-responses, described in the last 

 chapter, we have in this case also, 

 though not shown in the present 

 Fig. 85. Thermo-mechanical record, the post-inorteiii relaxation 



Curve obtained Photo- ,• ^i . .• r • 



graphically (Coronal Fiia- succeedmg the contraction of rigor 



ment of Passiflora) mortis. 



^"^.^^sh™" "rer/u™: In order to show that the mole- 

 but on reaching death- cular change which occurred at the 



point, at 59-6° C, there is . ^ . . • j j i.u 



a sudden inversion of the point of mversion was mdeed the 

 curve, due to spasmodic irreversible death-change, I took the 



death-contraction. ,1 • 



curve once more, after allowmg the 

 specimen to return to its original temperature. The curve 

 now obtained showed no reversal-point. 



Remarkable agreement between thermo-mechanical 

 curves of similar specimens. — It was pointed out in the last 

 chapter that the death-point is almost as definite as a phy- 

 sical constant. And not only is this true of the death-point, 

 which I fird in different phanerogamous specimens, under 

 normal conditions, to be almost invariably close upon 60'^ C, 

 but it is also more or less true of the whole curve, those given 

 by similar specimens being almost identical. In this way 



