940 



SCIENCE. 



[X. S. Vol. XXI. Xo. .547. 



ieal explanation of the ascent of water in 

 trees is a problem which must be mentioned. 

 The renewed investigations which have 

 been made along this line from an objective 

 point of view will undoubtedly contribute 

 to its eventual solution. 



It is a matter of interest that in their 

 studies of the physics of transpiration, 

 Brown and Escombe have found evidence 

 to regard this process also as a matter of 

 ditSusion through multiperforate septa, 

 rather than a matter of mass action. It is 

 calculated that by diffusion water may pass 

 out of the stomates to an extent as much 

 as six times the actual amoimt of trans- 

 piration which has been observed in special 

 cases. 



The great number of cytological investi- 

 gations which have been completed within 

 the past ten years indicate notable advance- 

 ments in a most important field; and this 

 is particularly true with relation to the 

 study of nuclear phenomena. Through 

 this work light has been thrown upon many 

 problems of cell physiology and of develop- 

 ment : and as a result of the latter new 

 theories of heredity have been advanced. 

 Nevertheless, the field for investigation has 

 been constantly broadened and many new 

 lines of research made possible. In spite 

 of the excellent results accomplished, there 

 is yet great uncertainty as to the interpre- 

 tations which have frequently been made. 

 In no field of work, perhaps, is it possible 

 for the personal factor to enter into the 

 results more largely than in this. Again, 

 it is unfortunately true that fixed material 

 has been studied almost to the exclusion 

 of all other and that even general observa- 

 tions relating to the conditions of growth 

 have been omitted in many instances. 

 IVIuch attention has been bestowed upon the 

 minutest details which seem to be of mor- 

 phological significance in the nucleus; but 

 often the purely physiological side has been 



iusufficientl}^ emphasized. It is quite pos- 

 sible that in different plants, the exact 

 method of chromosome division, or the 

 manner of nucleolar disappearance, may 

 not be similar: and it is cei'tainly well 

 knoAvn that external conditions may con- 

 siderably modify the details of spindle foi*- 

 mation, and perhaps other details in 

 nuclear and cell division. The important 

 point in every case is to determine if the 

 same physiological purpose may be accom- 

 plished. 



It is extremely important, however, to 

 the subject of physiology that the methods 

 Y. hich have made possible these cytological 

 advances shall be extended and utilized in 

 developing a knowledge of all of the vari- 

 ous activities of the cell. In this way, a 

 clearer insight may be given of many ab- 

 struse metabolic processes; and certainly 

 further light may be thrown upon the mat- 

 ter of protopla.smic decompositions and 

 secretions, the production of enzymes and 

 alkaloids, tannins and other products. Go- 

 ing hand in hand with observations upon 

 fresh material, the limitations of micro- 

 chemisti-y alone should determine the pos- 

 sibilities in this direction of the work. 



In such cytological investigations, Fisch- 

 er's work on the artificial production of 

 effects resembling those seen in fixed proto- 

 plasm should be borne well in mind. This 

 work is timely, and may assist in checking 

 irrational developments by forcing a proper 

 regard for a comparison of the effects ob- 

 served in fixed tissues with those shown by 

 the living material. 



There are, moreover, but few directions 

 in which the study of metabolism and 

 metabolic products may not profit from 

 cytological research. A notable instance 

 of what there is to be done is well indicated 

 by the work of the late Dr. Timberlake on 

 the division of plastids and the develop- 

 ment of the starch grain. 



