3.00 



Scientific Proceedings, Royal Dublin Society. 



Table XIII. 



Syringa vulgaris : leaves. 



Here the rise, owing to iusolation, is very marked, viz., from 17'12 to 

 25'68 atmospheres. Some of this, however, must be attributed to concentra- 

 tion by loss of water, as, at the end of the experiment, some of the leaves 

 had begun to wilt. Desiccation sbowed that this concentration could by no 

 means account for the total rise in osmotic pressure. Tlie observed change, 

 viz., from 69'16 per cent, to 63'5 per cent, of water, would account for a 

 change of depression of freezing-point from -l--t23°C. to -1-551°C., or a 

 raising of the osmotic pressure from 17" 12 to 18-66 atmospheres, leaving the 

 remainder to be accounted for by the formation of carbohydrates. 



Experiments 33, 34, 35 form another series, illustrating the effects of 

 assimilation and transpiration on the osmotic pressure. The leaves in tliis 

 case were gathered at 6 p.m., after a dull day, and kept in dark till II a.m. 

 next day. They were then divided into three lots — a, h, and c. The sap of 

 a was examined immediately as a control ; b was exposed to diffuse light for 

 four hours without water-supply ; c was exposed to diffuse light for four hours, 

 but the petioles were suj)plied with water. At the end of the four hours 

 the saps were examined. 



Table XIV. 



Syringa ■vulgaris : leaves. 



