Walter Stiles 
94 
nitrate absorb this salt so that (in the mean) the concentration inside 
the cells increases at the rate of about o-oo6 gram-molecule per hour. 
This is of the same order as the rate found by Fitting and Hofler for 
Rhceo discolor and Tradescantia elongata respectively. Thus, we have 
evidence that the order of intake of different substances is different 
with different tissues, for in the case of epidermal cells of Gentiana 
Sturmiana urea appears to be absorbed about 170 times as fast as 
potassium nitrate, but in the epidermal cells of the leaf of Rhoeo discolor 
at about the same rate, while Hofler finds for the stem parenchyma 
cells of Tradescantia elongata that potassium nitrate may be absorbed 
up to five times as fast as urea. 
It is also interesting that other cells of Gentiana Sturmiana do 
not show the same high rate of absorption 1 of urea, as the sub- 
epidermal cortical cells were found to absorb this substance so that 
its concentration inside the cells increases at the rate of about 0-002 
gram-molecules per minute. A similar difference between epidermal 
and cortical cells was also observed in Euphrasia Rostkoviana , 
Melampyrum sylvaticum, Veronica Beccabunga, Homogyne alpina and 
Taraxacum officinale. 
A high rate of uptake of urea, as well as of ethyl alcohol, anti¬ 
pyrin and tartaric acid, by the curious hairs extruded from the 
epidermal cells of the seeds of Cuphea lanceolata immersed in water, 
has been recorded by van Wisselingh (1920), but it is doubtful whether 
van Wisselingh’s experiments were rightly interpreted, for it is not 
at all certain whether we are here concerned with an action of the 
living cell or with reactions of a dead constituent of the epidermal 
cells (cf. Ruhland, 1922). 
1 Hofler uses the term permeability as practically synonymous with rate 
of absorption. 
(T0 be continued) 
