1892.] Noteworthy Anatomical and Physiological Researches. 55 
which are, on two sides, older leaves, and on the other two, 
thin layers of gum. As an instance of the third case the 
orthotropic position of folded palm-leaves is mentioned. It 
would scarcely seem permissible to put forward a case like this 
as an instance of special adaptation, for, as is well known, it 
is generally true that rolled-up dorsiventral organs are in- 
clined to take the erect position. Undoubtedly, nevertheless, 
such a position is of decided value to the young leaves and 
parts of leaves for it clearly serves to put them in the least 
exposed position with reference to the incident rays of a hot 
tropical sun. Many examples of this manner of protection 
may be found among the monocotyledons in particular. The 
last method of protection is a favorite one and is by no means 
confined to plants growing in the tropics. Uvaria, Gossyp- 
tum and Begonia are the examples cited by Potter. In each 
of these genera when a leaf has become old enough to resist 
the hot rays of the sun and the unfavorable conditions of the 
atmosphere it is quite natural that it should be utilised as a 
protecting shield for the immature leaves which are less able 
to withstand conditions varying so widely from the optimum. 
Some good figures are given in the plates which accompany 
the article, and, with the exception of the third, each class is 
illustrated. —Conway MACMILLAN. 
Vitality of ferns. 
: Wittrock publishes in a recent paper’ a series of observa- 
tions, which form together a very valuable contribution to the 
biology of the ferns. It deals especially with the ability of 
fern-leaves to imbibe water and to become fresh after a long 
¢pt dry for several months or even years and after being pre- 
taken. for ; rbarium specimens ! Professor Wittrock has 
ray sa instance, several species from the Pringle-collections 
t Sctleng them in water for some minutes and then planted 
N moist sandy soil, keeping them carefully in shade an 
u > 
nder an ordinary glass globe. The ferns became perfectly 
1 : er 
at = Wirrrock: De filicibus observationes biologicae. Acta horti Bergin, 
0. 8, Stockholm, 1891. 
