644 SUMMARY OF CURRENT RESEARCHES RELATING TO 
had, by hypertroj)hy, become leaves in structure and function. They 
may be compared to similar normal structure in other conifers, and 
must be regarded as primitive atavistic structures such as occurred in 
Leptostrobus. J 
Aerial Roots of Tseniophyllum.* — According to Prof. J. Wiesner, 
the aerial roots of Tseniophyllum Zollingeri, a leafless epiphytic Javanese 
orchid, have a remarkably slow growth, compared to that of the bamboo 
as 1 to over 2000. They grow in a nearly vertical direction, flat against 
the stem of the tree, and do not display any geotropic curvature. They 
are negatively heliotropic and hyponastic, which enables them also to 
grow on horizontal surfaces. Their growth appears to be entirely sus- 
pended in the dark. The plant has a remarkably lichen-like habit, the 
roots apparently performing all the functions of nutrition. 
Adaptation of Land-Plants to Existence in Water. j — Dr. R. Keller 
gives further illustrations of this phenomenon in the cases of Myosotis 
Pehsteineri, LytJirum salicaria , and Ficaria verna , describing the changes 
which take place ia the external form and in the internal structure of 
the various organs. 
j8. Physiology. 
(1) Reproduction and Embryology. 
Fertilisation in Pinus.J — Mr. V. H. Blackman gives an account of 
the cytological details and of the processes surrounding it, in Pinus 
sylvestris, from the formation of the ventral canal-cell to the period of 
cell-formation at the base of the egg. 
As the oosphere nucleus, after separation of the nucleus of the 
ventral canal-cell, moves rapidly towards the centre of the egg, it in- 
creases greatly in size, from the formation of a peculiar metaplasmic 
substance which fills up the nucleus and ultimately obscures the chro- 
matin. Almost the whole of the contents of the lower part of the 
pollen-tube passes over into the oosphere by the rupture of the closing 
membrane of the pit at the apex of the tube. At this stage all the 
four nuclei may be seen lying in the cytoplasm of the egg. The stalk- 
cell nucleus, the pollen-tube nucleus, and one generative nucleus, remain 
at the apex of the egg, and ultimately become disorganised. The other 
generative nucleus advances rapidly towards the female nucleus, and 
gradually penetrates its substance until it is almost completely enclosed 
within it. After fusion has taken place, the chromosomes can be dis- 
tinguished as two separate groups. No definite resting fertilised nucleus 
is formed. The spindle, which lies obliquely in the centre of the egg, is 
at first multipolar in form, and, while it is in this condition, the chromo- 
somes begin to split longitudinally, but can still be distinguished in tw’o 
groups. Only after the formation of four segmentation-nuclei do these 
begin to wander down to the base of the egg. The number of chromo- 
somes in the egg-nucleus is twelve ; and the same number were also 
found in the nuclei of the cells of the prothallial tissue and of the 
pollen-mother-cells. The chromosomes of the first segmentation-spindle 
* SB. k. Akad. Wiss. Wien, cvi. (1897) l te Abth., pp. 77-98 (1 pi.), 
t Biol. Centralbl., xviii. (1898) pp. 545-52 (10 fisrs.). Cf. this Journal, ante , 
441. + Proc. Roy. Soc., Ixiii. (189*) pp. 400-1. 
