226 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
cerned, though this is not true to the same extent of the root. No fresh 
initials are formed after the first stages of development within the 
embryo. The terminations of the tubes are not localized in a special 
tissue; but may occur in the middle of the parenchyme, below the 
palisade-cells, or in contact with the epiderm. 
The presence of the continuous laticiferous tubes above described 
does not exclude that of articulated tubes in the same plant ; the forma- 
tion of the former may precede that of the latter. 
Membrane of Bast-cells.* — Herr C. Mikosch has observed a struc- 
ture of the membrane of bast-cells in Apocynum Venetum which he 
considers confirmatory of Wiesner’s view f of the origin of the particles 
of the cell-wall from plasomes ; the structure is similar to that described 
by Strasburger in Vinca major. In addition to the usual thickening-layer 
consisting of numerous lamellse, there is an inner one sharply differ- 
entiated from it, composed of a number of nearly parallel rods placed at 
right angles to the axis of the cell. While the outer layer is composed 
of pure cellulose, micro-chemical tests show that the composition of this 
inner layer is not so simple. Very long treatment with concentrated 
sulphuric acid or ammonium copper oxide discloses the presence in the 
rods of granules which are evidently identical with Wiesner’s dermato- 
somes. The author sees no other possible explanation of the structure 
observed but that protoplasm takes part both in the formation and in the 
growth of the cell-wall. 
Commenting on this paper Herr E. Hanausek J points out that the 
presence of an inner layer in bast-fibres has been already described by 
himself and others in numerous instances. As a reagent for its demon- 
stration he prefers sulphuric acid and iodine, and considers that the 
reaction indicates the presence in it of albuminoids. 
Arrangement of Secretory Canals. § — M. P. Van Tieghem confines 
his researches on this subject to three natural orders, Dipterocarpeae, 
Simarubeae, and Liquidambareae. In his conclusions the author states 
that the primary secretory canals in these three orders belong, in the 
stem and root, to the periphery of the pith, and in the leaf to the periphery 
of the medullary region of the peridesm. The Liquidambareae differ 
from the Dipterocarpeae and Simarubeae in possessing circummedullary 
secretory canals beneath the phloem in the root. The Dipterocarpeae 
resemble the Simarubeae in the arrangement of their secretory canals, but 
are easily distinguished by their stratified phloem. Among the Diptero- 
carpeae, JDryobalanops aromatica is worthy of note, as it has in its petiole, 
besides the medullary canal of its median bundle, four external pericyclic 
or cortical canals ; and it is pointed out by the author that the genus 
Leitneria, which was placed among the Urticaceae by Bentham and 
Hooker, and among the Cupuliferae by Baillon, agrees with the Diptero- 
carpeae in the arrangement of its secretory canals. 
Limit of the Stem and Boot in the Hypocotyledonary Region. || — 
M. P. Van Tieghem states that the hypocotyledonary region of the 
embryo consists of two parts : the base of the stem or tigel, and the base 
* Her. Deutsch. Bot. Gesell., ix. (1891) pp. 30G-12. 
f Cf. this Journal, 1891, p. 207. t Ber. Deutsch. Bot. Gesell., x. (1892) pp. 1-4. 
§ Jouru. de Bot. (Morot), v. (1S91) pp. 377-88. || Tom. cit., pp. 425-8. 
