774 SUMMARY OF CURRENT RESEARCHES RELATING TO 



spicuous in the mistletoe. The division of the nucleus in the 

 embryo-sac takes place in the ordinary way. At each end of the 

 embryo-sac three cells are formed, three antipodals, two synergidfe, 

 and an oosphere. The seventh nucleus lies within the protoplasm 

 near the oosphere, and is remarkable for its size and its elongated 

 form ; this is the nucleus of the embryo-sac. At this period a small 

 vesicle is formed in the wall of the embryo-sac in close proximity to 

 the synergidae, into which vesicle the two synergidso project, destroy- 

 ing its wall at two spots ; the cell-wall which is thus destroyed 

 assumes a mucilaginous character, in the form of very slender threads, 

 arranged in the form of a cone, and constituting the peculiar " filiform 

 apparatus." The synergidae then also begin to exercise a destructive 

 effect on the outer part of the split wall of the embryo-sac ; at two 

 points, corresponding to the apices of the synergidae, openings 

 appear through which the pollen-tube can project free into the 

 interior of the sac. By careful pressure the " filiform apparatus " 

 can often be separated from the synergidge. The threads of the 

 latter coalesce, after fertilization, into long homogeneous semi-fluid 

 masses. 



The function of the synergidae is therefore to facilitate the aqcess 

 of the pollen-tube to the oosphere (germinal vesicle) by absorption of 

 the wall of the embryo-sac. All stages in the division of the nucleus 

 can very easily be followed out in the formation of the endosperm of 

 Viscum album ; they agree with those described by Strasburger in the 

 case of Hyacinihus orientalis. 



Action of Heat upon Vegetation.* — A short note upon this 

 subject by A. Barthelemy deals with (1) the action of heat upon the 

 development and direction of growth of roots, (2) the action of heat 

 upon the phenomena of heliotropism. 



1. One experiment was made upon hyacinths growing in vessels 

 of water ; it was found that they invariably grew towards a heated 

 brazier placed in their vicinity, whereas the leaves grew away from 

 the source of heat and towards the window which was brightly 

 illuminated. In another experiment a vessel of water was divided 

 by a glass partition into two compartments, one of which contained 

 hot water while in the other were placed hyacinth roots floating in 

 cold water; the roots always grew towards the glass plate, and 

 applied themselves closely to it. When the water was coloured by 

 means of lampblack it vras found that the growth of the roots 

 towards the heated compartment was checked — possibly on account 

 of the increased conductivity causing the temperature round the roots 

 to become more uniform, or by the lessening of the diathermancy 

 of the water which would hinder the action of the heat upon the 

 roots. 



2, The experiment made to show the action of heat upon helio- 

 tropism is described by the author as follows : — A pencil of solar 

 rays was made to fall either directly or by a mirror upon a Dipsacus 

 placed in a vase in a dark room ; the stalk rapidly bent towards the 



* Comptes Kendus, xcviii. (1884) pp. 1006-7. 



