Dixon — Note on the Spread of Morhid Changes, &fc. 209 



After seven days from the beginning of the experiment the leaves on 

 C and D, which before had shown the slight changes just mentioned, had 

 become quite withered and curled, and slight but similar changes were 

 becoming apparent in a few of the upper leaves of D. 



Fourteen day 8 later — i.e.,twenty-onefrom thebeginningof theexperiment — 

 there were still four living leaves on D\ but their veins were coloured red, 

 and the edges of two were discoloured and brown. The remaining leaves on 

 I) were dry and crisp. On C most of the lower leaves had fallen, and those 

 wliich were still attaclied were crisp and much discoloured. The remaining 

 u)>per leaves were apparently still quite healthy. 



The lower leaves on G were now removed ; and the lower 23 cms. (shaded 

 in tlie figure) of the branch were killed with hot water in the same manner 

 as the portion of B had been, while the upper healthy leaves were protected 

 by enveloping them in a damp cloth. Five days after this treatment all the 

 leaves on C were stained and curled, their cells being evidently dead. 



In this experiment we see that all the leaves above a length of stem of 

 23 ems. which has been killed by heat, show strongly marked morbid changes 

 after five days if no attempt is made to wash out the killed portion ; wliile in 

 a similar case in which the heated region is flushed 

 out with water, these changes are postponed for twenty- 

 one days, and even then are not complete. 



The experiment also demonstrates that leaves on 

 an uninjured branch may be caused to wither by 

 supplying them with water which has passed tlirough 

 a heated stem, although their normal supply is inter- 

 fered with in no other way. 



In the second experiment a pot-plant of Cotone- 



aster frigida was used (fig. 2). Distilled water was 



supplied at the cut end of the main stem ; below 



this four lateral branches. A, B, C, and B, took origin, 



separated from one anotiier by distances on the stem of 



18 cms., 5 cms., and 22 ems, respectively from below 



upwards. From each of tliese, leafy secondary branches 



sprang. B supported only one secondary branch ; and 



it was cut short by an old injury. was lopped at 



the beginning of theexperiment, and was left with only 



one secondary branch. B and ^ were not mteriere:d 'Plant of Cotonettster frijiida 

 „;fU used in Experiment 2. The 



dark portion on the main 



During twenty-four hours distilled water was stem indicates the region 

 supplied at the cut top of the main stem. Shortly ^^'^^ ^^^ ■^i^^^'l- 

 after this supply had been started, the region of the stem, viz., 22 cms. between 



