Problems of Plant Physiology 45 



stance of diastase, protease and ereptase of wheat and barley may 

 retain its activity for 20 years and after the power of germination is 

 lost (37, p. 390). Finely divided platinum and iridium among inor- 

 ganic substances cause a catalytic action resembling that of enzymes. 

 Buchner's discovery that the filtered sap of yeast plants can change 

 sugar to alcohol and carbon dioxide, is interesting in this connection. 

 The capability of diastase to hydrolize 10,000 times its volume of starch 

 and invert 100,000 times its volume of sugar shows its great power. 

 The yeast plant itself is active in various ways; thus it can reproduce 

 20 or 30 times in the absence of oxygen, it can produce alcohol up to 

 14 per cent before the yeast plant is killed, and it may produce a 

 pressure of 25 atmospheres of carbon dioxide in a closed vessel before 

 such action ceases (1, Bd. I, p. 576). Nageli (38) estimates that the 

 volume of a cell of beer yeast is about .000002 cubic centimeter and 

 weighs about .0000005 milligram. The great numbers, however, make 

 up for their diminutive size. 



Bacteria also show activity in some of these directions. A closed 

 flask, for example, containing a nutrient solution colored with indigo 

 carmine and inoculated with certain bacteria will lose the blue color 

 due to the removal of every trace of oxygen by the bacteria. On read- 

 mitting oxygen the blue color will return. In proportion to their bulk 

 some bacteria may use oxygen 200 times as fast as man (1, Bd. I, p. 

 526) . Certain bacteria will live in carbon dioxide under 50 atmospheres 

 of pressure and may burst tin cans of conserves by developing such gas 

 pressures. Small amounts of carbon dioxide thus given off may be 

 estimated conveniently by a method given by Hempel (39) and extremely 

 small amounts of carbon dioxide can be detected by the biometric method 

 for seeds and other objects as devised by Tashiro (40). 



The subject of phosphorescence presents an interesting field for 

 investigation. For the already voluminous literature, one is cited to the 

 recent work of Czapek (41), Molisch (42), and other contributors. 

 Whether one holds to the extracellular, intracellular, or other theory 

 regarding the production of light in different plant forms, various ques- 

 tions arise. The sudden increase or decrease in the strength of the 

 light emitted requires explanation, as does the effect of different pres- 

 sures of oxygen and the actual oxygen consumption by the organism 

 in its formation of light. The light intensity may be sufficient to pro- 

 duce clear photographs of various objects, to produce heliotropic curv- 

 atui'es, and to read by, especially when "bacterial lamps" (42) are 

 used, and is equivalent to about .000785 of a Hefner unit per square 

 meter. The meaning of the necessity of a large amount of sodium for 

 luminous bacteria is important as is also non-motility and light pro- 

 duction in certain forms (31, p. 213). 



Many interesting points regarding diffusion await solution. The 

 diffusion of gases ordinarily takes place comparatively slowly as shown 

 by Clausius (43, Bd. 3, p. 753) in connection with whose work the 

 theory of diffusion by Maxwell was founded. Ewart (44) has shown 

 that in certain cases diffusion causes the distribution of substances 

 more rapidly than streaming. Osmotic pressure varies only slightly 



