48 SUMMARY OF CURRENT RESEARCHES RELATING TO 



BOTANY. 



A. GENERAL, including the Anatomy and Physiology 

 of the Phanerogamia. 



a. Anatomy. 



CI) Cell-Structure and Protoplasm. 



Development and Function of the Cell-plate.* — After a historical 

 review of the subject, H. G. Timberlake gives an account of his own 

 observations on the development and function of the cell-plate in the 

 higher plants, his examples being taken from the growing root-tips of 

 various flowering plants, from pollen mother-cells, and dividing pollen- 

 grains. Among the more important results obtained are the following. 



The division of the cell-body is due to the activity of the kinoplasm 

 of the cell ; the splitting of the cell-plate, or at least its differentiation 

 into separate layers, is the essential act in the division of the cell-body. 

 According to the author, the whole of the substance of the fibres becomes 

 transformed into a portion of the cell-plate ; in other words, the cell- 

 plate is a result of a change of form of the substance composing the 

 fibres. The nucleus appears to be the centre of the metabolic processes 

 concerned in the production of the kinoplasm. The real centre for the 

 formation of the fibres is the chromatin. This is shown by the formation 

 of new radiating fibres round the daughter- nuclei in the root-tip of the 

 onion during the diaster stage, and by the formation of a spindle round 

 a single chromosome in the pollen mother-cells of Hemerocallis. In the 

 cells of the higher plants the kinoplasm appears to be formed round 

 the nucleus as a centre. In this form the kinoplasm takes part in the 

 process of nuclear division, and later divides the cell by a part of the 

 fibres being transformed into a membrane which becomes, in splitting, 

 the plasma-membranes of the daughter-cells. 



The carbohydrate material for the formation of the cell-wall appears 

 to be held in a reserve form in the protoplasm before it is actually needed 

 for the process of wall-formation. 



Development of the Karyokinetic Spindle in Vegetative Cells.f — 

 From a study of nuclear division in the root-tips of Allium cepa, Vicia 

 Faba, and Erythronium americanum, Amanda M'Comb maintains that 

 the process of spindle formation in vegetative cells of the higher plants 

 does not essentially differ from that of the reproductive cells. In both 

 cases the spindle-fibres, or at least the vast majority of them, are of 

 cytoplasmic origin. They may appear at first either in the form of a 

 weft about the nucleus, or may radiate from it. In the vegetative cells 

 the spindle primordium may be monaxial and strictly bipolar from the 

 first ; but it is often multipolar. No such organs as centrosomes or 

 centrospheres exist in the root-tips of Allium. 



Cones of the Multipolar Spindle.J— A. A. Lawson gives the following 

 as a summary of the phenomena connected with the origin of the cones 



* Bot. Gazette, xxx. (1900) pp. 73-99, 151-70 (2 pis.). 

 t Bull. Torrey Bot. Club, xxvii. (1900) pp. 451-9 (2 pis.). 

 X Bot. Gazette, xxx. (1900) pp. 145-53 (1 pi.). 



