THE DEATH- SPASM IN PLANTS 



157 



a vessel of this water, and as a further precaution against air- 

 bubbles clinging to the interior of the tube, the whole may 

 be put inside the receiver of an air-pump and subjected to 

 a repeated partial vacuum. The removal of air-bubbles may 

 also be effected by rinsing the tube of Allium in water 

 containing a small quantity of ether, and immediately after- 

 wards washing with ordinary water. This must be done, 

 however, with caution, as the presence of an appreciable 

 quantity of ether would be likely to affect the excitability of 

 the tissue. Before commencing the experiment, it is advis- 

 able to allow the specimen to 

 remain immersed in water for 

 about half an hour, by which 

 time it becomes fully turgid. 



The lower end of the Allium 

 tube filled with water is closed 

 by a piece of solid glass rod, 

 and the upper end is also closed 

 with a piece of glass tube, 

 having a capillary bore. A 

 graduated scale is placed behind 

 this latter, so as to measure the 

 movement of the water- index, or 

 this movement may be con- 

 tinuously recorded on a revolving 

 drum (fig. 156). The Allium preparation is now placed in a 

 vessel of water, and subjected to a gradual rise of temperature 

 in the manner already described. 



If, at the temperature corresponding to death, there 

 should now be a sudden excitatory contraction of the Allium 

 tissue, the volumetric change thus produced will force out 

 the contained water, and we shall observe a relatively rapid 

 expulsive movement of the water-index. From the curves 

 given above in fig. 82, it will be seen that this occurs at 

 a temperature of 59 C. in a younger, and at 6f C. in an 

 older specimen. Previous to this, there was an inward 

 movement of the water-column corresponding to the gradual 



Fig. 82. Determination of Death- 

 point in Allium Tube by Ob- 

 servation of Volumetric Con- 

 traction, causing sudden Expul- 

 sion of Water 



A, record given by older specimen ; 

 death-point 63 C. B, record 

 of younger specimen ; death- 

 point 59 C. 



