AND DEW BY THE GREEN PAKTS OF PLANTS. 



321 



6, On the Power of Absorption by detached Leaves laid on the 



Surface of Water. 



Of the preceding experiments, the results were solely judged of 

 by the general appearance as presented to the eye. Such, how- 

 ever, clearly proved that leaves can readily act as absorbing 

 organs in the absence of roots, not only to nourish themselves, 



but oth 

 baceous. 



leaves on the same shoot, especially if the stem be her- 



In the following experiments the leaves were left as stated 

 below from July 30th to August 3rd, 1878. They were all care- 

 fully weighed to the 5000th part of a gramme, then again at the 

 latter date. The losses are reduced to percentages of the original 

 weight of the specimens respectively. 



Proportional 



no. of Surface on 



>* 



11 



11 



11 



11 

 11 



Plant. stomata. 



Ber beris aqu ifo Via [0 



50 



„ ,, In air. 



Fiats Carica 



100 



In air. 



Ligustrum mi Iff are 



» if ^° 



„ In air. 



Prun us Lau roceras vs... 



20 



... In air. 



Aitcuba javon ica 



50 



In air. 



Hcdera Helix 



45 



In air. 



Water. 



Upper. 

 Lower. 



Upper. 

 Lower. 



L T pper. 

 Lower. 



ii 



it 

 ii 



L T pper. 

 Lower. 



ii 



ii 



it 



ii 



Upper. 

 Lower. 



ii 

 ii 



it 



Upper. 

 Lower. 



Loss 

 per cent* 



2fr31 



13*38 



4910 



1-52 



5-23 



73-95 



7 -93 



1*73 



5333 



13 72 



451 



2139 



5 97 



9-82 

 27-84 

 10-82 



16 64 (gain) 

 1026 



Apparent 

 condition. 



Fresh. 



Fresh. 



Withered. 



Fresh. 



Fresh. 



Dry and brittle. 



Fresh. 



Fresh. 



Flaccid. 



Fresh. 



Fresh. 



Fresh. 



Fresh. 



Fresh . 



Slightly puckered. 

 Fresh. 



Fresh. 



Fresh. 



These specimens illustrate the fact that, unless the difference 

 be very pronounced, the eye cannot judge of the amount of water 

 a coriaceous, or even not always a herbaceous, leaf may have lost; 

 secondly, that the loss is not entirely dependent upon, nor pro- 

 portional to, the relative amount of stomata on the surface. In 

 some cases, certainly the more often, there is less loss when the 

 lower side is on the water ; but even then this may not be refer- 

 able to the stomata more than to a less cut icularized condition of 

 the surface. 



In the next series, in each case one specimen was partly plunged 

 in water, the cut end (as in every experiment), as well as some 

 leaves, were elevated in the air. They remained thus from July 



