560 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
y. General. 
Mechanical Effect of Rain on Plants.* * * § — From observations made 
in Java, Herr J. Wiesner altogether disputes the injurious effects alleged 
to be produced on leaves and flowers even by tropical rain. He never 
observed any splitting or tearing of leaves or petals even by the heaviest 
rain, when not accompanied by strong wind. When flowers or leaves 
are bodily torn away by rain, it is because their tissues had already 
undergone the change which made them nearly ready to fall. The im- 
munity from the effects of heavy rain is due to the elasticity of the 
flower-stalk or leaf-stalk. If these organs are fixed so as to have no 
power of movement, the impact of a falling body of only one-thousandth 
the weight of a heavy drop of rain will have a destructive effect. A 
moderately heavy rain has no effect on the leaves of Mimosa pudica. 
Freezing of Plants.^ — From a series of observations made on 
tropical plants, Herr H. Moliscli states that the freezing of plants at a 
temperature above zero (C.), independently of their transpiration, is the 
result of chemical rather than of physical changes in the living substance ; 
some chemical processes, such as the formation of chlorophyll and of 
etiolin, respiration, and the assimilation of carbon dioxide, being largely 
dependent on the temperature, while other processes are not. 
B. CRYPTO GAMI A. 
Cryptogamia Vaseularia. 
Parthenogenesis in Marsilia.J — Mr. W. R. Shaw lias succeeded in 
cultivating embryos of Marsilia Drummondii from female protliallia in 
which the archegones were completely isolated from any possible access 
of anthcrozoids. About one-half of the megaspores thus sown ger- 
minated. The embryos were slightly smaller than those produced in 
the ordinary way. 
Regeneration of Selaginella.§ — Dr. J. Behrens describes the two 
modes of regeneration which occur in Selaginella, especially in S. in - 
sequalifolia, viz. by the independent growth of fragments of the stem, and 
by proliferation of the sporange. 
Muscineae. 
Hygroscopic Mechanism of the Peristome of Mosses.[| — Herr C. 
Steinbrinck compares the mechanism by which spores are thrown out of 
the sporange of a Moss with those which govern the bursting of a capsule 
or an anther in flowering plants. Like seeds, the spores of mosses are 
usually protected against rain by the outer teeth forming a dense cover- 
ing over the mouth of the sporange, due to the hygroscopic movements 
of its outer teeth. But in some cases the dissemination of the spores is 
promoted by rain. According to the behaviour of the peristome-teeth 
on drying, Mosses may conveniently be classified under three groups, 
* Ann. Jard. Bot. Buitenzorg, xv. (1897) pp. 277-353. 
t SB. K. Akad. Wiss. Wien, cv. (1896) pp. 82-95. 
i Bot. Gazette, xxiv. (1897) pp. 114-7. 
§ Flora, lxxxiv. (1897) Erg'anzbd., pp. 159-66. 
|| Tom. cit., pp. 131-58 (13 figs.). 
