ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 689- 



the presence of darkly staining, rod-like bodies in the cytoplasm, which 

 are apparently of kinoplasmic origin, and appear to be connected with 

 mitosis ; their function has not yet been fully determined. The cyto- 

 plasm is distinctly fibrillar, but this aspect disappears when the spindle 

 is formed. The spindle originates partly from the linin of the nuclear 

 network, but mostly from the fibres which surround the nucleus as the 

 wall dissolves. It is narrow and pointed with spreading fibres. The 

 chromatin is at first inconspicuous, but later on forms paired masses 

 which are regarded as chromosomes. Synapsis is a normal phenomenon, 

 and the separation of the chromosomes is of the lieterotype character. 

 The reduced number of chromosomes is sixteen. The character of the 

 chromosomes rendered it impossible to make out the features of the 

 second mitosis, but it is essentially different from the first. 



Embryology of Rhizophora Mang-le.* — M. T. Cook has studied the 

 embryology of Rhizophora and finds that only one out of four ovules is 

 fertilised. There are probably four megaspores. Completion of the 

 embryo-sac is accompanied by disintegration of the nucellus, and later 

 on the inner integument and the endosperm likewise disintegrate. The 

 embryo has a distinct suspensor and has three periods of growth : (1) first 

 growth of cotyledons ; (2) growth of the hypocotyl ; (3) second growth 

 of cotyledons. During the first period part of the embryo and endo- 

 sperm are forced out of the embryo-sac into the ovary chamber, while 

 during the second period the cotyledons are much modified for the 

 purpose of absorption. During the third period the cotyledons elongate, 

 and their point of union with the hypocotyl extends beyond the apex 

 of the ovary. 



Physiology. 

 Nutrition and Growth. 



Ascent of Water in Trees.! — A- J- Ewart continues his investiga- 

 tions upon the ascent of water in trees, and is of the opinion that con- 

 tinuous ascent is only possible in living wood, for even without mechanical 

 blocking of the vessels the power of conduction is lost rapidly after death. 

 The author concludes that in tall trees the living cells maintain the 

 conditions for ascent of water, and only in trees over 20-50 m. in 

 height is pumping action necessary. No vessels appear to run as open 

 channels from end to end of the tree. In the trees used for experiments 

 there were no continuous suspended water columns or high internal 

 tensions, and this fact, coupled with the high total resistance, seems to 

 indicate that the resistance is overcome locally, and not by enormous 

 tension from above or pressure from below. The author's experiments 

 show that the ascent of water is a vital problem, since it is dependent 

 upon conditions only possible in living wood. 



Self-sterility of Flowers. $—L. Jost has investigated self -sterility of 

 the flowers of Coryd(dis cava, G. lutea, Secale cereale, Lilium hulhiferum, 

 Hemerocallis flava, Gardamine pratensis, and a few of the Leguminosse. 



* Bull. Torrey Bot. Club, xxxiv. (1907) pp. 271-7 (2 pis.). 

 t Proc. Eoy. See, Ixxix. (1907) pp. 395-6. 

 i Bot. Zeit., Ixv. (1907) pp. 77-117 (1 pL). 



