ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 533 



Electromotive Properties of the Leaf of Dionaea.* — Professor 

 J. Burdon Sanderson has investigated the immediate and subsequent 

 electrical results of excitation of the leaf of Dioncea, which have pre- 

 viously been examined by Munk, Kunkel, and the author himself. 



It is found that at the moment of excitation (whether mechanical 

 or electrical) the under surface of the lobe of the leaf is electro-nega- 

 tive to the upper surface, the difference of potential reaching its maxi- 

 mum about half a second after excitation ; it then rapidly decreases 

 until the upper surface is ultimately electro-negative to the lower, and 

 this after-effect remains constant for some time. With a current not 

 much more than adequate, excitation occurs at the moment of closing 

 the current, but none occurs on breaking the circuit unless the current 

 be sufficiently strong. The author considers (1) that the difference 

 of potential is due to the electromotive forces which reside in the 

 living protoplasm of parenchyma- cells in contact with one another, and 

 in different states of physiological activity ; (2) that the second phase 

 of excitation is probably dependent on the diminution of turgescence 

 of the excited cells, arising from a migration of liquid ; (3) this 

 explanation cannot be accepted for the phenomena of the first phase, 

 the sudden accession and rapid propagation of which show that it is 

 probably analogous to the " negative variation " or " action current " 

 of animal physiology. 



Influence of a Galvanic Current on Growing Roots.j — F. Elfving 

 has observed the effect of a continuous current of electricity upon the 

 growing organs of plants, especially roots, and finds that it causes a 

 distinct curvature of the organ in the direction of the positive pole. 

 This curvature has not, however, any physiological significance, like 

 those due to geotropism and heliotropism ; it is due to the retarding 

 effect on growth of the current of electricity, especially on that side 

 of the organ which the current meets directly. 



B. CRYPTOGAMIA. 



Cryptogamia Vascularia. 



Schizaeacese.J — The second part of Prantl's work on the Vascular 

 Cryptogams is devoted to this group of ferns, and especially to the 

 morphology of the non- sexual generation. 



The first section is occupied with the arrangement of the leaves on 

 the stem and the structure of the leaves and stem. There occur both 

 radial and dorsiventral stems, the most remarkable among the latter 

 being Lygodium, which has a single dorsal row of leaves, this arrange- 

 ment originating even in the growing point. A similar structure 

 occurs also in other ferns. 



The genus Lygodium is also of special interest with respect to the 

 structure of the sporangia. Each sporangium is here enclosed in a 

 pocket, the upper wall of which is composed of the surface of the leaf 



* Proc. Roy. Soc, xxxiii. (1882) pp. 148-51. 

 t Bot. Ztg., xl. (1882) pp. 257-64 ; 273-8. 



% Prantl, K., ' Unters. zur Morphologie der Gefasskryptogamen. Heft ii. Die 

 Schizfeaceen.' Leipzig, 1881. 



