in 



ASCENT OF SAP IN STEMS 



67 



In this experiment we see that all the leaves above a 

 length of stem of 23 cm. which has been killed by heat, 

 show strongly marked morbid changes after five days, 

 while in a similar case, if the heated region is washed out 

 with water, these changes are postponed in some 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 through a heated stem. 



In another experiment a plant of Cotoneaster frigida was 

 used. Distilled water was supplied at 

 the cut end of the main stem. Below 

 this four lateral branches, A, B, C, and 

 D, took origin, separated from one 

 another by distances on the stem of 

 18 cm., 5 cm., and 22 cm., respec- 

 tively, from below upwards (see 

 Fig. 12). From each of these leafy 

 secondary branches sprang. D sup- 

 ported only one secondary branch, and 

 it was cut short by an old injury. C 

 was lopped at the start of the experi- 

 ment, and left with only one secondary 

 branch. B and A were not interfered 

 with. During twenty-four hours dis- 

 tilled water was supplied at the cut 

 top of the main stem, and meanwhile 

 the region of the main stem, viz., 

 22 cm., between C and D was killed 

 with hot water as before, while the leaves were suitably 

 protected from injury. 



Three days later blotchy discolorations appeared on 

 the lower leaves of D, and less markedly on some of those 

 of A, B, and C. 



On the fourteenth day the four lowermost leaves of D 

 were completely discoloured, and a small blotch had 



F 2 



