48 SUMMARY OF CURRENT RESEARCHES RELATING TO 



carbohydrates, as mucilage and pectin, and oils and other substances, take 

 up these stains. Finally, if the substance in the cell-wall which takes 

 up the stain is protoplasm, what is it in the starch-grain ? 



Nuclear Reduction and Fertilisation in Paris and Trillium.* — 

 A. Ernst has investigated the chromosome reduction, embryo-sac de- 

 velopment, and fertilisation in Paris quadrifolia and Trillium grandi- 

 florum. In Paris the reduction in the number of chromosomes is from 

 24 to 12, and this takes place at the first division of the embryo-sac 

 mother-cell. This division is of the characteristic heterotype, and 

 results in the production of two cells, the lower of which becomes 

 directly the embryo-sac, while the upper, after a second division of its 

 nucleus, degenerates. In Trillium the reduction is from 12 to 6 

 chromosomes (the smallest number known in the vegetable kingdom, 

 and found also in Naias), and of the two cells formed the upper 

 usually degenerates without division, while the lower becomes directly 

 the embryo-sac. The heterotypic division was studied, and the synapsis 

 stage, which the author believes to be a natural condition, was observed. 

 The chromosomes of this division in both plants often show, in the 

 equatorial flake stage, indications of a second longitudinal division. In 

 the diaster stage, by separation of the two halves of the daughter- 

 chromosomes, produced by this second division, V-, U-, and -shaped 

 figures are often produced. When the daughter- nuclei are reconstituted, 

 this second division becomes lost, but a fresh longitudinal splitting of 

 the chromosomes is to be observed when the nuclei divide again. All 

 the divisions in the embryo-sac were found to be exactly similar, so that, 

 in contrast to Lilium, Fritillaria, and Tidipa, the normal reduced num- 

 ber of chromosomes is found even in antipodal nuclei. Double fertilisa- 

 tion was observed in both cases, but actual fusion of the three nuclei 

 appears to take place only on the spindle, for in all three the beginning 

 of a definite chromatin thread was observed while they were in contact 

 but yet unfused. The facts that in the vegetative cells of Trillium 8 

 chromosomes, instead of the normal 12, were sometimes to be observed, 

 and that the number of chromosomes in Paris is exactly double that 

 of Trillium, when compared with the variations in number among the 

 genera of the Liliaceas, suggest that the chromatin thread of the nucleus 

 undergoes a successive, and not a simultaneous division. 



Nucleus of Spirogyra.t— C. van Wesselingh has added yet a fourth 

 to his papers on the nucleus of this alga. In this contribution he 

 pays special attention to the question of the nuclear wall and spindle, 

 and the behaviour of the vacuole-wall during karyokinesis. By slowly 

 killing dividing cells, and by the use of 20 p.c. chromic acid solution, 

 combined with staining, he was able to prove that the spindle consists 

 of a number of similar threads, which surround the nucleus and are 

 combined together to form numerous bundles. The spindle-threads do 

 not grow through the nuclear wall, but the latter disappears at an early 

 stage, and the spindle is at first multipolar, but later becomes bipolar. 

 The observations were made on Spirogyra informis. 



* Flora, Erganzungsband, 1902, 46 pp. (6 pis.). 

 t Bot. Zeit., lx. (1902) pp. 115-38 (1 pi.). 



