134 TRANSACTIONS OF THE [SEss. LXxv, 
the leaves, then it seems that a whole series of complex 
adaptations have been prepared to utilise all this rich 
air-food. 
But here I am on very delicate and dangerous ground. 
Is it possible for rain-water with dissolved salts to enter 
the leaf ? 
That question has been debated, often with great violence, 
for something like 179 years. Naturally, I do not wish to 
dogmatise on this difficult pomt. But several of the best 
authorities on vegetable physiology admit that such absorp- 
tion does take place. Both Sachs and apparently Vines 
agree that this is possible. Pfeffer remarks as follows: 
“Dem Gemiss koénnen sehr wohl kleine Quantitaéten von 
gelésten Stoffen mit Regen und Thautropfen in die Blatter 
gelangen.” I do not find Kny’s (21) experiments in the least 
conclusive. They have been often quoted as showing that 
no such absorption takes place, but the following extract 
seems to me to show that such absorption can take place 
even under very heroic treatment: “ Die in Oel steckenden 
besprengten Zeigten beginn des Welken; die in Oel steck- 
enden nicht besprengten waren stark welk.” Neither 
Liebig nor indeed anyone supposes that such absorption 
can be large in amount. It is probably only a very minute 
proportion of the water that enters by the roots. 
Nevertheless, when one remembers the rich manurial 
value of this dust, that it is carefully strained out of the 
rain by a whole series of elaborate contrivances, and also 
that there are neat arrangements for encouraging mites 
to reside permanently on the leaves, one can only draw 
the conclusion that mites, bacteria, and rain-gutters in the 
leaves form together one of the most interesting cases of 
symbiosis that has yet been discovered. 
AUTHORITIES. 
(1) Lunpstrom.—Acta Nova Upsal., ser. 3, xiii., 1886-1887 ; Bot. 
Centralblatt, 1886, p. 282, and 1890, p. 246. 
(2) De WinpemMann.—Com. Rend., 1904, pp. 551 and 913. 
(3) ZIMMERMANN.—Ann. Jard. B. Buitenzorg, xvii., 1900-1. 
(4) Prona.—B. Soe. Geol. Ital., xxiii., 1904. 
(5) Von LaGERHEIM.— Bot. Centralblatt, 1892, p. 238. 
(6) Matmr.—Svenska Vet. Akad. Handl., Bd. xxv., 1900. 
(7) LorsreneR.— Biolog. Centralblatt, Bd. xiii., 1893. 
(8) ScHUMANN.—Pringsheim, Jahrbuch, xix., 1888. 
(9) Lupwic.—Biologie d. Pflanzen, 1888. 
