506 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
the incidence of strong light appears to be the most important factor. 
The mode of falling off often differs greatly in nearly allied species. 
The whole of the hair is never completely thrown off ; a rudiment 
always remains behind. 
Formation of Balls of Roots.* * * § — Prof. J. Sachs discusses the 
“balling” of the roots of plants grown in pots or wherever the supply 
of soil is insufficient. It depends on the excessive lengthening and 
ramification of the root-filaments, without any correspondingly large 
development of root-hairs. The injurious effect of this balling on the 
growth of the plant is due partly to the interference with respiration, 
caused by the crowding of the roots ; partly to the insufficient supply 
of nutriment consequent on the difficulty with which water penetrates 
through the dense mass of roots ; but chiefly to the fact that the root- 
hairs are prevented from coming into contact with the particles of soil 
on which they are dependent for their nutriment. 
Roxburghia.l — Herr Y. Lachner-Sandoval has exhaustively examined 
the structure of several species belonging to this genus. In B. javanica 
he finds that the arrangement of the parts of the flower is such as to 
facilitate self-pollination, and to render cross-pollination very difficult. 
In the embryo-sac no antipodals could be detected. One of the 
synergidae frequently increases in size along with the fertilized oosphere, 
and clothes itself with a cell-wall. The author sees no sufficient ground 
for maintaining the Roxburghiaceae as a distinct group from the Liliaceae. 
Their one distinguishing character is the monocarpellary pistil. The 
basal placentation is a peculiarity of the genus Boxburgliia alone. 
/3. Physiology. 
(1) Reproduction and Embryology. 
Embryogeny of Gnetum.J — Herr G. Karsten has studied the 
processes which go on within the embryo-sac in the East Indian species 
of Gnetum , viz. G. Gnemon , neglectum, and edule , and three undescribed 
species, and compares them with the corresponding phenomena in 
Casuarina , as observed by Treub.§ Sections of the female flowers were 
made by Jung’s microtome, and coloured by picro-carmine. 
The inner integument of the ovule developes into a long tube 
leading to the apex of the nucellus, and projecting far beyond the other 
two integuments ; this forms at its apex a drop of sweet fluid which 
captures the pollen-grains carried by the wind or possibly by insects. 
The outer very thick integument becomes fleshy and bright-coloured, 
and is attractive to herbivorous animals. In the division of the cells 
of the nucellus at an early stage, there is no evident predestination of 
one, as there is in most Angiosperms, to be the mother-cell of the 
embryoHsac. In G. Gnemon and neglectum there are usually two, three, or 
even more embryo-sacs which appear equally capable of further develop- 
ment ; while in G. edule and allied forms only one was seen. In the 
division of the contents of the embryo-sac (in all the species examined) 
* Flora, Ixxv. (1892) pp. 171-82. 
t Bot. Centralbl., 1. (1892) pp. 65-70, 97-104, 129-35 (1 pi.). 
% Bot. Ztg., 1. (1892) pp. 205-15, 221-31, 237-46 (2 pis.). 
§ Cf. this Journal, ante, p. 230. 
