ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 773 



Geotropism and Hydrotropism of Roots.* — A. Tomaschek main- 

 tains that the degree of geotropism in a root does not depend on the 

 rapidity of growth ; nor is it afl'ected even by severe injuries, pro- 

 vided the apex of the root is left uninjured. He regards the view of 

 Darwin as fully established that the receptivity for the influence of 

 gravitation resides in the apex of the root only, and moreover that the 

 apex is susceptible to psychometric differences in the environment 

 (hydrotropism), and that this susceptibility is conveyed to the adjacent 

 parts. 



Water-glands and Nectaries-f — W. Gardiner confirms Sachs's 

 view that the exudation of water from water-glands is entirely due 

 to root-pressure, and never takes place with cut organs ; although in 

 some cases (Fuchsia globosa) an abundant exudation from hairs in the 

 vicinity of the water-glands gives the appearance as if it proceeded 

 from the latter. Light retards very considerably the exudation of 

 water both from water-glands and from those secreting epidermal 

 structures which, are not dependent on root-pressure. Water-glands 

 are, as a rule, much more fully developed in Dicotyledons than in 

 Monocotyledons, which may be due to the latter being of a more 

 generally aquatic habit. The chief function, both of water-glands 

 and of thin-walled epidermal cells placed in connection with a 

 vascular bundle, is to allow of the escape of superfluous water, which 

 would otherwise cause injection of the intercellular spaces, and even 

 rupture of the tissue. 



Nectaries, i. e. structures of whatever morphological value de- 

 signed to secrete a saccharine fluid, do not, as Sachs has pointed out, 

 discharge their nectar in consequence of root-pressure, but from the 

 activity of the cells of the nectary themselves. 



Folds of Cellulose in the Epidermis of Petals.^ — E. Kohne 

 describes a number of different ways in which the lateral cell-walls 

 of the epidermal cells of the petals are thickened and folded in a 

 variety of plants. He discusses the purpose of these foldings, and 

 believes it to be merely mechanical, in strengthening the epidermal 

 layer of cells. 



Anatomical Structure of Cork-woods.§ — A. Gehmacher gives a 

 detailed account of the anatomical structure of several extremely 

 light woods from the tropics known as " cork-woods," viz. Alstonia 

 scholaris from India, Bomhax Buonopozense from Senegal, B. Geiba, 

 B. pentandrum from India, Eriodendron anfractuosum from India, 

 Kerminiera Elaphroxylon from the White Nile, and the very beautiful 

 Chinese "cork-wood," which comes apparently from the root of a 

 Conifer. They all belong to the wood itself, and not to the bark. 



"Filiform Apparatus" in Viscum album. || — W. Scrobischewsky 

 describes the " filiform apparatus " of the embryo-sac as very con- 



♦ Oesterr. Bot. Zeitschr., xxxiv. (1881) pp. 55-9. 

 t Proc. Catnb. Phil. Soc, v. (1884) pp. 35-50 (2 pis.). 

 t Ber. DeutBcli. Bot. Gesell., ii. (1884) pp. 21-9 (1 pi.). 

 § Oesterr. Bot. Zeitsclir., xxxiv. (1884) pp. 149-55. 



II SB. Vers. Rus. Nuturf. u. Acrzte, Odessa, Aug. 24, 1883. See Bot. Centralbl 

 xviii. (1884) p. 156. 



