ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
221 
Among the more general results obtained are that in Pinus there is 
a continuity between the secreting canals of the leaf and those of the 
cortex of the stem ; each foliar bundle, when it enters the stem, is 
accompanied by two secreting canals. Secreting tubes are very widely 
distributed in seedling Conifers, and consist of intercellular spaces, 
usually situated below the epiderm in the pericycle and the pith. The 
foliar bundle is frequently accompanied by a vascular wing, composed 
of transfusion tissue, which attains its greatest development in the 
Cupresseae. This forms an independent circulating system, after the 
foliar bundle itself has lost its function of carrying sap from the root. 
The augmentation in the number of cotyledons in many Gymnosperms 
appears to result from the division of two large cotyledons, which have 
broken up into a number of equivalent structures. 
Root of Arborescent Liliacese.* — M. H. J. de Cordemoy describes 
a remarkable development of metaxylem in the root of Lomatophyllum 
borbonicum, Dracaena marginata , and Cohnia fiabelliformis. The large 
vessels of metaxylem, proceeding from the differentiation of conjunctive 
cells of the central cylinder, develope not only on the internal margin 
of the phloem-bundles, but also on that of the protoxylem-bundles, 
which they prolong towards the centre of the root, and also in the 
medullary parenchyme properly so called. These vascular bundles 
disturb in a remarkable way the symmetry of the central cylinder of the 
root. 
In the root of Dracaena marginata the secondary formations originate, 
not from the pericycle, but from the cortex. There is in these cases a 
centrifugal increase in the size of the central cylinder, causing a rupture 
of the endodermal ring, and bringing the pericycle into contact with the 
secondary cortex. A communication is thus established between the 
primary and secondary conducting systems, i. e. between the central 
cylinder and the cortical zone. 
Anatomy of Combretacese. — Herr II. Heiden j* gives a full account 
of the structure of the various organs in this natural order, followed by 
descriptions of all the genera and of a number of the species. Among 
the more noteworthy characters are the usually bicollateral structure of 
the vascular bundles ; the vessels with bordered pits even in the walls in 
contact with the medullary rays ; the absence of mucilaginous epidermal 
cells ; the wood-parenchyme with simple pits ; the absence of special 
auxiliary cells to the stomates ; and the invariable presence of simple 
unbranched and unicellular but two-chambered hairs. 
Herr C. Holtermann J also describes the structure of a number of 
genera and species of Combretacese, but finds very few general characters 
which distinguish them from the allied orders. 
Anatomy of Afromendoncia and Mendoncia.§ — According to Herr 
E. Gilg, the splitting of the xylem in these genera of Acanthaeeae is 
due to the formation of wedges of leptome. The medullary cambium is 
* Bull. Soc. Bot. France, xl. (1893) pp. 42-6, 145-7. 
f Bot. Centralbl., lv. (1893) pp. 353-60, 385-91 ; lvi. (1893) pp. 1-12, 65-75, 
129-36, 163-70, 193-200, 225-30 (1 pi.). 
+ ‘ Beitr. z. Anat. d. Combretaceae,’ 47 pp., Bonn, 1893. See Bot. Centralbl., lvi. 
(1893) p. 305. § Ber. Deutsch. Bot. Gesell., xl. (1893) pp. 351-64 (1 pi.). 
