206 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
showing graphically the degree of variation to which the numbers of 
parts are subject in plants. The examples taken are chiefly the number 
of ray-flowers in the capitule of certain Composite, and the number of 
rays or branches to the umbel of certain Umbelliferse. 
j8. Physiology. 
(1) Reproduction and Embryology. 
Acrogamous and Basigamous Fertilisation.* * * § — M. P. Yan Tieghem 
calls attention to the fact that the normal polarity of the so-called 
“embryo-sac” is occasionally reversed. The ordinary position of the 
“ egg-apparatus ” and of the antipodals is invariable in those plants in 
which the mother-cell of the endosperm (embryo-sac) is produced 
within the nucellus of a tegumented ovule, with its apex turned towards the 
micropyle, whether the mode of impregnation is porogamic or chalazo- 
gamic. But in certain of the Loranthaceae, in which the mother-cell of 
the endosperm arises on the inner surface of the carpel, and where there 
is therefore neither placenta nor ovule, the oosphere and the synergids 
are located at the lower, the antipodals at the upper end of this mother- 
cell. A similar phenomenon is presented by the genus Arceuthobium, 
which the author proposes to remove from the Loranthaceae, and to make 
the type of a new order Arceuthobiace^, intermediate between the 
Loranthaceae and Santalaceae, where two endosperm-mother-cells are 
produced at opposite spots in the ovarian cavity, and where, therefore, 
there is a placenta, but no ovules. This mode of impregnation the 
author terms basigamous , in contrast to the ordinary acrogamous mode. 
It occurs again in some of the Balanophoraceae with naked ovules, a 
reversion apparently to an archaic type, where it is accompanied by 
chalazogamy. This phenomenon appears to be in harmony with that 
observed by Tretiakof f in Allium odorum , where the antipodal cells 
may sometimes assume physiologically the part of embryonic vesicles. 
Physiology of Reproduction.^: — Prof. G. Klebs gives a resume of 
recent observations on the phenomena of sexual reproduction and of 
non-sexual propagation. He sums up in favour of the view that the 
universal original mode of multiplication was non-sexual ; the sexual 
mode, when once established, entirely superseded the non-sexual in all 
the higher animals, and became also the ordinary mode of multi- 
plication in most of the higher plants, in consequence of the advantage 
afforded by the union of the slightly dissimilar properties of the two 
parents. 
Structure and Growth of the Pollen-tube.§ — Mr. A. J. Ewart 
records the results of a series of observations on the mode in which the 
pollen-tube makes its way through the tissues of the style. In some 
plants — Narcissus , Lilium, Tulipa , Scilla — minute round or oval pores 
were detected in the apex of the pollen-tube, through which solid 
particles had been extruded. These particles probably consist of 
granules of a zymogen, by means of which the tube disintegrates the 
* Journ. de Bot. (Morot), ix. (1895) pp. 465-9. 
t Cf. this Journal, 1895, p. 450. 
X * Ueb. einige Probletne d. Phys. d. Fortpflanzung,’ Jena, 1895, 26 pp. 
§ Proc. Liverpool. Biol. Soc , ix. (1895) pp. 189-204 (1 pi.). 
