1256 Journal of Applied Microscopy 



die appears to be bipolar from the beginning, but no bodies that could be inter- 

 preted as centrospheres were found. Although tripolar spindles were occasionally 

 met with, Smith is certain that they are not normal stages in the development of 

 the spindle, and comes to the interesting conclusion that the spindle in Osmunda 

 does not pass through a multipolar stage. To the reviewer the evidence for such 

 a conclusion would have been more convincing had the appearance of tripolar 

 spindles been accounted for or had more stages in the formation of the cones of 

 the bipolar spindle been figured. 



For fixing the material chrom-acetic acid and Flemming's weaker solution 

 were employed. Chloroform was used to precede the infiltration of paraffin. 

 The stains that gave the most satisfactory differentiation were iodine-green and 

 acid-fuchsin, and safranin and gentian-violet. A. A. Lawson. 



Brown, H. T., and Escombe, F. Static Diffusion The authors investigated the laws gov- 



of Gases and Liquids in Relation to the As- • j-rc • ..u i. n 



similation of Carbon and Translocation in ^''^^"g diffusion through very small 



Plants. Phil. Trans. Roy. Soc. of London, apertures. They find that : 



193: 223-292, 1900. ^^^ ^j^g amount varies directly as 



the diameter of the orifice. This holds for openings 5 or 6 mm. or less in diam- 

 eter. It follows that diffusion through holes 1 mm. or less is very rapid per unit 

 of area. 



(2) When the distance between the holes is ten times the diameter of the 

 holes themselves, the amount of diffusion is the same as when a septum is 

 wanting. 



(3) These laws hold for both solutes and gases. 



By analogy with the lines of force about an electrified disc, the investigators 

 have reached the same conclusions mathematically. 



Applying these results to plant structures the authors conclude that : (a) The 

 open stomata of a normal mesophyte (^Helianthus anmms) are sufficient for the 

 diffusion of several times as much CO 2 as the plant actually uses. There is no 

 need then for more stomata. (b) The limitation of the amount of CO 2 absorbed 

 is to be looked for in the resistance to diffusion offered by the cell wall, (c) 

 The stomata are sufficient to account for transpiration, (d) The translocation of 

 foods is probably more largely a phenomenon of diffusion than was supposed, 

 since .7 per cent, of opening in cell walls would permit 30 per cent, of free dif- 

 fusion. The paper confirms Blackman's results (1895), and discusses the physi- 

 cal laws underlying them. T. C. Frye. 

 Chicago. 



The Martha's Vineyard Summer Institute, Hyde Park, Mass., announces the 

 summer session of the School of Nature Study to be held during July and 

 August, 1901. Besides the School of Natural Study the Institute embraces 

 Schools of Methods, Oratory, Languages, Mathematics, Science, and Art ; in- 

 formation concerning which may be obtained from the President of the Institute, 

 Dr. Wm. A. Mowry, Hyde Park, Mass. 



