202 SUMMARY OF CURRENT RESEARCHES RELATING TO 



there and can be seen to be made up of very numerous granules. In 

 an early anaphase the staiuable contents have quite disappeared, and 

 finally the blepharoplasts break up entirely into numerous granules, by 

 which time the two daughter-nuclei in the central cell have been fairly 

 well organised. The granules fuse to form a band, while the daughter- 

 nuclei reach a resting condition and form the spermatid cells, each of 

 which is then metamorphosed directly into a spermatozoid. The bands 

 form a helicoid spiral around the spermatid, and in a very early stage 

 protuberances can be distinguished in its outer surface which ultimately 

 grow into cilia. 



Meanwhile, the grain ends of the pollen-tubes have grown dow r n and 

 come to hang free in the archegonial chamber. In fertilisation they 

 push against the neck-cells and finally burst and discharge the spermato- 

 zoids over the archegonia. The fluid in which the sperraatozoids swim 

 is certainly derived in part from the pollen-tube, and may be partially 

 formed by extrusion from the egg-cell. The mature spermatozoids are 

 the largest known to occur in any plant or animal, and are visible to 

 the naked eye. They are ovate or nearly spherical ; their motion is 

 mainly by means of the cilia, but they have also a sort of selective 

 amoeboid motion of the spiral end. The entire spermatozoid enters the 

 egg-cell, swimming in between the ruptured neck-cells; the cilia-bearing 

 baud remains at the apex of the cell while the nucleus passes on and 

 fuses with the egg-nucleus. At the same time the spermatozoid cyto- 

 plasm fuses with the egg-cytoplasm. The first division of the egg- 

 nucleus was not observed, but the second and later divisions were 

 carefully studied. In no case has any centrosome been noticed. The 

 cilia-bearing band has certainly no function in tbe formation of the first 

 cleavage spindle, or the spindles in any of the divisions immediately 

 following, as it remains intact at the apex of the egg-cell until the egg- 

 nucleus has divided into very many small nuclei ; it disappears later. 

 It appears to be simply a mechanism for transference of the functional 

 male cell, and not comparable with centrosome or centrosphere, as it is 

 located entirely outside of the spindle, and has no connection with the 

 spiudle formation. It is moreover limited to the division of a single 

 cell, no similar organ appearing in any other stage of the plant's develop- 

 ment. 



Nutrition and Growth. 



Development of Sauromatum guttatum Schott. * — K. Genau de- 

 scribes an experiment in which this Himalayan Aroid was grown from 

 the tuber up to complete opening of the flower without receiving any 

 external supply of water. Plants were grown both in the light and 

 dark ; in the former case the plant began to wither after about five 

 weeks, having lost in the meantime 21 • 5 p.c. of its weight. In the dark 

 the plant grew for six weeks before beginning to wither and lost only 

 17 p.c. of its weight. The tuber contains a very large amount of water 

 (over 84 p.c. was found in one examined) which is protected from 

 evaporation by a thick periderm immediately inside which is a layer of 

 parenchymatous cells rich in mucilage. 



* Oesterr. Bot. Zeitschr., li. (1901) pp. 321-5. 



