220 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
the pith the development of the mucilage is completed about the period 
of blossoming, and it may then take as much as five years to become 
completely absorbed. After its first formation it becomes gradually 
differentiated into layers. 
As regards its function, the accumulation of mucilage is to be 
regarded neither as an excretory product nor as a reserve food-material, 
but probably as a contrivance for the storing up of water. 
Secondary Wood of the Apetalae.* — By the use of histological 
characters derived from the structure of the wood, M. C. Houlbert 
classifies the natural orders belonging to the Apetalae into eight families, 
having but little genetic affinity to one another. Of these eight families, 
five, viz. the Urticaceae, Piperaceae, Polygonaceae, Chenopodiaceae, and 
Proteaceae, have a superior, the remaining three, viz. the Cupuliferae, 
Santalaceae, and Aristolochiaceae, an inferior ovary. The special 
features presented by transverse, radial, and tangential sections are de- 
scribed in the case of a large number of genera and species. The 
Proteaceae are divided into three sections, the Banksia , the Orites, and the 
Protea groups. Nearly related to the Proteaceae are the Elaeagnaceae, 
Myricaceee. and Casuarineae ; while the Thymeleaceae are much more 
remote. With the Piperaceae may be associated the Chloranthaceae and 
Garryaceas. The Chenopodiaceae are divided into two groups, the 
Amarantheae and Chenopodieae, with the Phytolaccaceae, Batideae, and 
Nyctagineae as allies. The Myristicaeeae show strong affinities to the 
Polygonaceae. The Urticaiceae are divided into two groups, the Urti- 
coideae and Ulmoideae. The Salicineae are nearly allied to the Cupu- 
liferae through the Betulaceae. The Cupuliferae themselves may be 
divided into two groups, the Betuloiaeae and Castaneoideae. The 
Juglandeae are allied to the Cupuliferae, while the true position of the 
Platanaceae is much more obscure. 
As a resume, the general plan of structure of the wood is usually 
uniform within a family. The woody parenchyme diminishes as the 
number of vessels increases, and vice versa ; and the thicker the woody 
fibre the broader are the medullary rays, and vice versa. 
Seedlings of Coniferae.t — Following Van Tieghem’s classification,! 
M. P. A. Dangeard divides Conifers firstly into those with inverted and 
those with erect ovules, and the former again into four sub-tribes, viz. 
(1) Pineae, with one pericyclic secreting canal in front of each vascular 
bundle ; (2) Cedreae, with an axile secreting canal ; (3) Araucarieae, 
with several pericyclic secreting canals in front of each bundle, the 
secreting canals of the leaves being cortical; (4) Podocarpeae, re- 
sembling the Araucarieas, but the secreting canals of the leaves peri- 
desmic. In the Pineae and Cedreae the ovary has two ovules, in the 
Araucarieae and Podocarpeae only one. In all Conifers with inverted 
ovules the root has secreting canals in its primary structure ; those with 
erect ovules include the Cupresseae and Taxeae. Detailed description 
of the anatomical structure of the seedling is given in the case of a 
number of species belonging to the genera Pinus, Picea , Larix, Tsuga, 
Araucaria , Cupressus, Actinostrobus, Thuja , and Taxus. 
* Ann. Sci. Nat. (Bot.), xvii. (1893) pp. 1-183 (8 pis.). 
t Le Botaniste, iii. (1893) pp. 126-204 (6 pis). Cf. this Journal, 1890, p. 479. 
X Cf. this Journal, 1892, p. 61. 
