718 NOTES 



Experiments carried out in the open air in the month of August gave the following 

 values for the transpiratory activity of 1 sq. dcm. of Leaf surface: 



Aesculus - - - - 

 ( lorylus - - - 

 Pyrus .... 



According to these figures the time for which the epidermis could cope with the 

 loss of water by transpiration would be as follows : 



Aesculus .... 2 hrs. 13 mins. 

 Corylus .... 43 ,, 



Pyrus ----- 39 



The above estimate is based on the actual rate of transpiration exhibited by cut 

 shoots standing in water, and hence with their stomata open. Since, however, 

 the stomata close (in the plants experimented upon) when wilting begins, it is better 

 to calculate on the basis of cuticular transpiration ; the latter was calculated, for 

 the aforesaid plants, by estimating the transpiration (during 24 hours, at 18 to 

 19 C, in air of relative humidity 70 per cent, to 75 per cent.) of leaves which were 

 first allowed to wither slightly, and were then hung up with the cut end of the petiole 

 waxed. Under these conditions the leaves withered very little more during the first 

 24 hours (except in the case of Corylus, where the marginal teeth shrivelled some- 

 what). The quantities of water lost by cuticular transpiration alone were as 



follows : 



Per 24 hrs. Per hr. 



Aesculus - - - - -18 g. -0075 g. 



Corylus - -407 -017 



Pyrus ... . -562,, 023 



From these figures we get the following values for the ratio of cuticular to total trans- 

 piration : 



Aesculus -r^. 



Corylus - - - - - - ^ 



Pyrus 



I0'6 



Assuming, as before, that the epidermis gives up one-half of its total water-content 

 to the mesophyll, the time for which the combined epidermal layers could cope with 

 the cuticular transpiration of the leaf is found to be : 



For Aesculus - - - - 16 hrs. 36 mins. 

 ,, Corylus - - - - 5 ., 52 



Pyrus .... 7 2 



While these figures are far from exact, they give a rough idea of the water-storing 

 capacity of the ordinary epidermis in certain cases. 



G4. Antkocyanin. Von Mohl : Vermischte Schriften, pp. 375 sqq. G. Haberlandt : 

 Sitzb. Wien, 72, 1876. Kerner v. Marilaun : Nat, Hist, of Plants. Vol. 1. Kny : 

 Atti. d. congr. hot, int. 1892. Stahl : Ann. Buit. 13, 1896. 



65. Tannin. Warming : Pot, Centr. 16, 1883, p. 350. Focke : Kosmos, 10, 



(protection against Fungi). Stahl : I.e. [52]. 



66. Raciborski : Flora, 1895 (Erg.-Bd.). 



