ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
67 
(3) Structure of Tissues. 
Anatomy of the Casuarinese.* — Mr. L. A. Boodle and Mr. W. C. 
Worsdell have studied the structure of Ihe tissues of the Casuarineae, 
with especial reference to their relations with the Gnetacem and with 
the Cupuliferse. 
The chief peculiarities of the structure of the stem were found to be 
the great development of xylera-parenchyme in the form of concentric 
bands, and the very broad medullary rays, sometimes occupying one- 
third of the circumference of the stem. The tracheal part of the xylem, 
consisting both of vessels with numerous and with single perforations, 
together with fibrous tracheids, resembles that of the Cupuliferae and 
other low forms of Dicotyledons. The vessels of the primary and early 
secondary wood are different from those in the later-formed wood, and 
show characters of a preceding type [szc] of structure. The phloem is 
-dicotyledonous in structure. Transfusion-elements occur in the ridges 
of the young stem and in the leaves ; but they have evidently a different 
origin from the transfusion-tissue in the leaves of Gymnosperms. In 
the young stem an external endoderm was found extending round the 
outer limit of the cortical bundles and dipping beneath the furrows. 
The structure of the seedling agrees with that of other dicotyledonous 
plants. 
In the structure of its phloem, Casuarina shows no important 
deviation from the dicotyledonous type ; and in its xylem-elements it 
agrees pretty well with the Cupuliferae and other Dicotyledons. It is 
in the disposition of the xylem-parenchyme, &c., that it shows the greatest 
peculiarity. 
Several new points in the structure of Gnetum are also described, viz. 
the presence in the wood of two kinds of vessel, with different modes of 
perforation, and the great difference between the structure of the node 
and that of the internode. 
Secondary Xylem of the Proteaceae.f — M. G. Houlbert proposes a 
classification of the genera of Proteaceae according to the histology of 
the secondary xylem, which he represents as also largely in accordance 
with their natural affinities. This structure shows a degree of simplicity 
which is probably an indication of an archaic origin. The three groups 
are as follows: — (1) Group of Banksia ; vessels in concentric zones, 
forming complete vascular arcs; (2) Group of Orites ; vessels in con- 
centric zones forming incomplete vascular arcs, terminated by paren- 
chymatous wings ; (3) Group of Protea ; vessels in concentric zones in 
the initial layers of the spring wood, irregularly scattered in the autumn 
wood. In each group the special characters are given of the various 
genera. 
Secondary Tissues of Arborescent Monocotyledons.^ — According to 
M. H. J. de Cordemoy, while in some arborescent Monocotyledons 
( Dracaena , Cordyline , Lomatophyllum ) the secondary formations become 
lignified and perform a supporting function, in others they play a very 
* Ann. Bot., viii. (1894) pp. 231-64 (2 pis.). Cf. this Journal, 1894, p. 220. 
f C.R. Ass. Fran^. pour l’Avancement des Sci., 1894, pp. 544-57. See Bot. 
Centralbl., lx. (1894) p. 208. 
J Comptes Rendus, cxvii. (1893) pp. 132-4. Cf. this Journal, 1893, p. 652. 
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