68 
Keeble . — The Hanging Foliage of 
shape of the twelve red-brown leaflets was 2*045 g. ; therefore 
the relative areas were 
green leaves 2*3 
red leaves 2*045 
Hence the rates of transpiration of equal surfaces : 
green 130 _ 130 
red-brown 48 x 2*3 54 
2-045 
So that the green leaves transpire more than twice as rapidly 
as the red-brown. In order to test the reliability of this 
potometer-method, the results obtained by it were checked 
by the ordinary method of weighing at intervals the branches 
under comparison. Thus, in the case just quoted, it was 
found by the potometer that the relative rates at which the 
young red-brown leaves and the older green leaves took up water 
were as 130:54. Their petioles were removed from the potometer, 
and were again cut under water, so that each now bore six 
leaflets. These petioles were fitted by means of halved corks 
into tubes containing water and weighed. They were weighed 
again after half an hour. The weighings showed the relative 
loss of water in the green leaf and red-brown leaf respectively 
to be as 3 : 1. Conceding that the relative areas of these two 
sets of six leaflets differ but little from those of the two 
sets of ten leaflets which the petioles originally bore, the 
relative areas of the two sets (vide supra) are as 2*3 green : 
2*045 red. Hence by the weighing method the relative losses 
of water by equal surfaces of red-brown and green leaves = 
red-brown _ 1 _ 1 _ 54 
green — 3 X 2-045 2*66 144 
^3 
£4 
and this agrees sufficiently well with obtained by the 
potometer. 
Since, then, the older, fully-grown leaves of Ambers tia 
nobilis transpire much more rapidly than the young hanging 
red leaves — and yet these latter show, by withering, ill effects 
