396 Groom. — On the leaves of Lathraea Squamaria 
In all these cases, the considerable development of the water- 
excreting apparatus in subterranean parts is to be correlated 
with the fact that the nature of the environment of these 
parts is such as to depress or entirely arrest transpiration 
underground. 
It has been frequently suggested that both the dome- 
shaped glands and the capitate hairs absorb nutrient liquids. 
Mr. Gilburt made a few experiments, and obtained evidence 
of the absorption of salts when supplied to these structures, 
and he therefore concluded that they naturally absorb solu- 
tions found in the soil. But a glance at Mr. Gilburt’s 
statistics shows that the absorption of the salts was ex- 
ceedingly slow, and in some instances could not be detected 
at all. I therefore regard his statistics as pointing out that 
the absorbent activity of the glands and hairs is so incon- 
siderable that we cannot suppose it to be of any fundamental 
importance to the plant. My own limited experiments 
confirm this view. By the use of very dilute solutions of 
gentian violet, by plasmolysis with common salt solution, or 
by staining with iodine (potassic-iodide solution) placed on 
an intact leaf of Lathraea , it was easy to show that the 
epidermis lining the pocket is more permeable to solutions 
than is the exposed epidermis. But only occasionally did 
I get any signs of a more rapid absorption of liquids by the 
dome-shaped glands than by the adjacent epidermal cells. 
Object of the pocket-hke form of the leaf. Cohn (4) sug- 
gested that these leaves might entrap and digest small 
organisms living in the soil, but he dismissed the view, as 
did Krause (5), Schcrffel (1), and Heinricher (6) : their 
evidence, together with the fact of the slow rate of absorption 
of liquids by the glands and hairs, is sufficient to show that 
the concavity of the leaves has nothing to do with the 
formation of a trap. I believe that the form of the leaf is 
adapted to protect the water-excreting glands (and possibly 
the capitate hairs), and is associated with the subterranean 
mode of life. The glands and hairs on the subterranean 
leaves have to contend; not only with climatic changes of 
