854 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
Structure of Loasaceae.^ — Herr R. Racine describes tlie histological 
structure of the wood of this natural order of plants, which differs in 
some respects from the nearly allied CucurhitacesB. The cambium-ring 
is closed, and displays only limited increase in thickness ; the vascular 
bundles are arranged in a single circle, and are collateral in structure ; 
the number of bundles is almost always twelve. The development of 
the flowers is also described. 
Dioscoreacese.'f — Herr E. Bucherer describes the anatomical and 
histological characters of this natural order, especially in reference to 
the genera Dioscorea and Tamus. The structure is described in detail 
of the tuber, the stem and the root, special attention being paid to the 
differences in the distribution and structure of the vascular bundles 
in the tuber and in the stem. Tubers occur in Dioscorea sinuata, 
D. Batatas, Tamus elephantipes, and T. communis. 
(4) Structure of Organs. 
Monochasia.J — Dr. K. Schumann describes various instances of this 
mode of inflorescence, especially those occurring in the genus Corchorus. 
He defines a monochasium as a system of shoots in which the axis of 
the first order is closed, and the axis of the second order takes up its 
continuation ; the continuation of this being again taken up by the axis 
of the third order, and so on. Since there is no possibility of a transi- 
tion between an axis of the first and one of the second order, every 
shoot-system, at least in the case of flowering plants with closed buds, 
must be either a monopodium ^or a sympodium. 
Picker el-weed Pollen. § — Prof. B. D. Halsted describes the pollen 
of the pickerel-weed [Pontederia cordata). It is trimorphic, and the 
relative size of the pollen-grains in the three forms corresponds to the 
relative length of the styles. The difference in size between the largest 
and the smallest grains is the greatest yet described for any flower, 
being about 8:1. 
Phylogeny of Amentacese. || — Dr. L. Celakovsky discusses the 
phylogenetic development of the different families of Amentaceae. The 
diflerences are the result of reduction, both in the vegetative and the 
reproductive organs. As respects the former, the lower portion of 
the lateral shoots is reduced, and the shoots become purely repro- 
ductive ; and this reduction attains a higher degree when the upper 
reproductive portion of the main shoots is also reduced, and uniaxial or 
monocaulic plants become biaxial or diplocaulic. Reduction of the 
reproductive organs is shown by the hermaphrodite flowers becoming 
either male or female. 
Four stages can be distinguished in the phylogenetic development of 
the Amentaceae, viz.: — (1) The fertile shoots are all alike, and the 
flowers hermai)hrodite (prehistoric) ; (2) the foliage-leaves are rudi- 
* ‘Zur Kenntniss d. BliitenentwickeluHg u. d. Gefaesbiindelverlaufes d. 
Loasaceen,’ Rostock, 1889, 8vo, 46 pp. and 1 pi. See Bot. Centralbl., xl. (1889) 
p. 392. t Haeulein u. Luerssen’s Biblioth. Bot., Heft 16, 35 pp. and 5 pis. 
t SB. K. Breuss. Akad. Wiss., xxix. (1889) pp. 555-84 (1 pi.). 
§ Bot. Gazette, xiv. (1889) pp. 255-7 (1 fig.). 
II SB. K. Bobm. Gesell. Wiss., 1889, pp. 319-43 (1 pi.) (German resume^. 
