GO SUMMARY OF CURRENT RESEARCHES RELATING TO 



BOTANY. 



A. GENERAL, including the Anatomy and Physiology 



of the Phanerogamia. 



a. Anatomy. 



(1) Cell-Structure and Protoplasm. 



Influence of the Nucleus on the Growth of the Cell. * — A further 

 series of experiments on non-nucleated cells of Spirogyra bellis have led 

 J. J. Gerassimow to the following results. 



The growth of cells containing an unusually large amount of nuclear 

 uubstance exceeds the average growth of the ordinary uninucleated cell ; 

 the cell-walls, the chlorophyll-bands, and apparently also the protoplasm 

 grow more energetically. The division of these cells is usually delayed, 

 and does not commence until tbey have attained a larger size. Non- 

 nucleated cells are capable of growing in length, though only to a small 

 extent. Their turgor at first increases, diminishing when they die. The 

 extensibility of their lateral walls is less than in the ordinary nucleated 

 cells. Non-nucleated cells under the influence of the nucleus of adjoin- 

 ing cells grow for a longer period and more energetically than other 

 non-nucleated cells. Cells which contain an unusually large amount of 

 nuclear substance are capable of conjugating both with one another and 

 with ordinary cells, whether one or the other is a male or female cell. 

 The size of the resulting zygotes is directly proportionate to the size of 

 the conjugating cells, and therefore to the amount of nuclear substance 

 in them. 



Reduction of Chromosomes in Larix leptolepis.f — Prof. 0. Ishikawa 

 has made the following observations. 



The nuclei of the young pollen mother-cells are characterised by the 

 presence of a loose knot ; a rather large oval or round nucleole is usually 

 found at this stage. At the next stage the separate chromosomes are well 

 developed, and are usually united in pairs, of which there are twelve. 

 They then contract ; pairs often uniting at one or both ends and forming 

 a variety of different figures. The stainability of the chromosomes 

 gradually increases, while that of the nucleoles diminishes. The nuclear 

 membrane and the nucleoles now disappear, and the pairs of chromo- 

 somes arrange themselves in the equatorial plane of the spindle. Then 

 they disperse in pairs to the opposite ends of the spindle, forming 

 different figures, finally separating from one another. The daughter- 

 chromosomes take a U or V form, and gradually travel towards the two 

 poles. 



When they reach the poles the arms of the chromosomes separate 

 from one another, twelve pairs being thus again formed. But this separa- 

 tion lasts only for a short time, for the separated arms again unite, not 

 only at the broken, but also at the other ends, thus forming twelve ring- 



* Bull. Soc. Imp. Nat. Moscou, 1901, pp. 1S5-220 (2 pis. find 3 figs.). Cf. this 

 Journal, 1900, p. 475. f Beih. z. Bot. Ceutralbl., xi. (1901) pp. 6-7. 



