ADDENDA. 141 



and to seal the tube, Murbach's third method seems faulty both in 

 that it is impossible to obtain pure carbon dioxide from the lungs, and 

 also because carbon dioxide is not a neutral gas but exerts active poison- 

 ous effects upon the living seeds. 



10 (page no). Far better for this purpose is a differential thermo- 

 stat which I have had made, but too late for full description in this work. 

 It consists essentially of a strip of thick copper having at each end large 

 cold- and hot-water boxes, and ten chambers large enough to hold each a 

 Zurich germinator along its length. When cold water from a tap is kept 

 circulating through the cold box, and the water in the other is heated 

 by a bunsen flame controlled by a Reichert regulator, the ten interme- 

 diate chambers keep a perfectly even gradation of intermediate temper- 

 atures, which may be held constant for days together, and which maybe 

 made to differ in greater or lesser amount by altering the heat from the 

 burner and by changing the rapidity of circulation of the cold water. 

 In this instrument it is possible to determine very accurately the mini- 

 mini, optimum, and maximum temperatures for germination of seeds 

 and early growth of the seedlings, and moreover several kinds can be 

 observed at once. The chambers communicate by small openings so 

 that water to supply the germinators stands at the same height in all of 

 them, and it is supplied at the desired height from a self-regulating 

 apparatus such as is ligured earlier in Fig. 27, page 109. 



Page 41. A method of making a gas-tight, joint with a living plant is 

 given by Arthur and MacDougal, in " Living Plants and their Prop- 

 erties " (New York, Baker and Taylor, 1898), 126. 



Page 51. Distilled water is never to be used for mounting living cells, 

 since endosmotic action becomes active and does them more or less 

 injury. 



Page 76. A simple dynamometer adapted to measure the power ex- 

 erted by swelling seeds, etc., and which is to be used with the precau- 

 tions mentioned in Note 3 above, is described by Richards inTorreya, I. 8, 



Page ror. Add to the Literature, Arthur and MacDougal, " Living 

 Plants and their Properties," especially Chapters VIII, IX, and X. 



Page 102. The auxanometer should be used to determine the grand 

 period of growth in some such structure as a flower-scape. It is instruc- 

 tive to compare the growth in this way of two similar parts, one in 

 light and the other in darkness. 



<j 



Page 134. Add to the Literature, Arthur and MacDougal, "Living- 

 Plants and their Properties," especially Chapters I, II, and IV. 



