406 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Where this appearance is presented, as in the Cucurbitaceae, it results 
from the apposition of two vascular bundles, of which one is often 
incomplete, consisting of phloem only. In some Cucurbitaceae he 
found these bundles to be for a certain distance complete, containing 
xylem also. 
Lenticels.* * * § — Herr C. von Tubeuf criticises Wieler’s conclusion that 
the pneumathodes on the roots of ferns are not true organs of aeration 
or respiration. The direct stimulus to the formation of these organs 
appears to lie in the moisture by which they are surrounded ; their 
growth then proceeds without fresh stimulus, provided it is not checked 
by dry air ; it very soon ceases if the necessary supply of moisture is 
not provided ; but water in the liquid state is not necessary for their 
production or development. 
Glands of Rutacese.t — Prof. G, Haberlandt finds, in all the species 
of Rutaceae examined, and especially in J Ruta graveolens , that the hypo- 
dermal glands are emptied by the bending of the leaf. The apparatus 
is composed of two constituents, the gland-lid and the gland-wall. The 
former is usually composed of four lid-cells which are metamorphosed 
epidermal cells. The separation of these cells is effected by a similar 
contrivance to that of the guard-cells of the young stoma. The flat 
usually more or less thick-walled cells of the wall of the gland exercise, 
by their strong turgor, a pressure on the contents of the gland, causing 
its sudden emptying when the leaf is bent. 
Phylogeny of TJlmacese.J — M. C. Houlbert has followed out in 
•detail the development of the wood in the different genera of Ulmaceae, 
especially in TJlmus , up to the tenth year, when it has acquired its 
characteristic structure, which it preserves during the rest of its ex- 
istence ; and points out the relationship to the (Jrticaceae, Moraceae, 
Boehmeriaceae, and other allied orders. 
Anatomy of Tradescantia.§ —Prof. A. Gravis gives a detailed account 
of the minute anatomy of Tradescantia virginica , especially of the tran- 
sitional region between stem and root. He regards the hypocotyl as the 
region where the root-strands join the foliar strands ; there is no passage 
between them ; but one type is substituted for the other type in the 
course of the hypocotyl. The so-called cauline bundles of the stem are 
in reality the sympodes formed by the bases of the leaf-traces. 
(4) Structure of Organs. 
Symmetry of the Floral Axes.|| — According to M. H. Ricome, a 
dorsiventral structure exists in a large number of branches of inflo- 
rescences which originate obliquely ; this is shown in the form and 
* Forst. Naturw. Zeitschr., 1898, pp. 405-14. See Bot. Ztg., lvii. (1899) 
2 t# Abth., p. 56. Cf. this Journal, ante , p. 171. 
f S.B. k. Akad. Wiss. Wien, Dec. 15, 1898. See Bot. Centralbl., Ixxvii. (1899) 
p. 263. 
X Rev. Gen. de Bot. (Bonnier), xi. (1899) pp. 106-19 (2 pis. and 5 figs.). 
§ * Rech. Anat. et Phys. s. 1. Tradescantia virginica,’ Bruxelles, 1898, 304 pp. 
and 27 pis. See Journ. r f Bot., xxxvii. (1899) p. 22S. 
|| Ann. Sci. Nat. (Bot.). vii. (1899) pp. 293-396 (4 pis. and 14 figs.). Cf. this 
Journal, ante, p. 55. 
