1895.] Anatomical and Physiological Researches. 113 
contains results of great interest and valuable suggestions for 
further investigations. It was a problem the author under- 
took to investigate in the moist climate of Java, but in order 
to prepare himself for this, he made some experiments in 
Austria and the results are recorded in the present paper. 
The relation between leaf-shape and rain-fall in tropical re- 
gions, where moisture and heat prevail, has already been 
studied by Stahl, Jungner and others. But the direct me- 
chanical effect of rain upon the plants and the power of re- 
sistance possessed by them against this factor has so far not 
been taken into consideration. 
It is well-known to cultivators that many plants are only 
able to thrive when they obtain a certain amount of water, 
and that several species die if they get too much. The full- 
grown leaves of the potato-plant decay and young leaves on 
autumnal shoots of certain trees are destroyed, when ex- 
posed to excessive rain-fall. We know, however, from am- 
phibious plants, that there is a great difference in regard to 
the ability of plants to withstand the effects of water. We 
have, also, learned by water-cultures that the roots of ter- 
restrial plants thrive in water, while the aerial parts of these 
Same plants die when they become submersed. In order 
to test this varying power of resistance against water, the 
author made the following experiments: 
Shoots cut from various plants were placed upon a sieve 
machia Nummularia and Tradescantia zebrina kept fresh for 
four weeks, and some hot-house Selaginelle were healthy 
even after an exposure to eight weeks steady rain. It was 
observed during the same experiment that the youngest leaves 
decayed first and then the oldest, while those which were in 
their greatest vigor were the last ones to decay. Solanum 
tuberosum was an exception, the very youngest leaves show- 
ing the greatest power of resistance. A similar result was 
obtained by submersing shoots in basins where a constant 
current of water was flowing. Shoots of the same plants died 
much sooner if they were submersed in stagnant water. 
There was also observed to be a great difference in regard to 
