J. H. Priestley 147 



when coal gas in high concentration displaces the air normally present 

 around and within the plant, secondary effects may well be produced, 

 such as asphyxiation, as found by Kosaroff(7) in his experiments with 

 hydrogen and carbon dioxide. 



The Nature of the Injuries produced by Traces of Coal Gas. 



In the normal flowering plant investigators are agreed that the organ 

 most sensitive to the toxic action of traces of the gas, is the root (5,1,3). 

 The normal leafy stem appears to be very little affected. Knight and 

 Crocker (G) have drawn attention to the extraordinary sensitiveness of 

 etiolated pea epicotyls, whilst Harvey (4) has shown that the growing 

 leaves of Ricinus are exceedingly sensitive and Crocker and Knight (2) 

 report similar behaviour with the flower buds of carnation. The reactions 

 of these sensitive plant structures occur at astonishingly low concentra- 

 tions of the gas and thus support the earlier observations of German 

 workers on the deleterious effects produced by laboratory air con- 

 taminated w^th small quantities of unburnt gas, upon the growth of 

 etiolated seedlings of the pea, vetch, or lentil (9, 15) and upon the etiolated 

 shoots of the potato (16). 



As the result of a great deal of work, mainly by the investigators 

 quoted above, there is general agreement both as to the structural effects 

 produced upon the plant and as to the constituents of the gas responsible 

 for the effect. There is also agreement that the actively growing organs 

 of the plant are far more sensitive than resting structures. 



In the case of roots, tubercles near the tip of the growing root are 

 reported by Doubt (3) and Harvey and Rose (5), a lessened growth in 

 length together with local increase in girth is reported by MoHsch(8), 

 Richards and McDougal(i4), whilst both Molisch(8) and Harvey and 

 Rose (5) report irregular curvatures in the root. Similarly in the case of 

 the etiolated stem, Neljubow{9) reported and Knight and Crocker{6) 

 confirm, a series of reactions on the part of the plants which develop 

 progressively with rising concentrations of the gas. These reactions in 

 order are (1) reduction in rate of growth, seedHng remaining erect, 

 (2) diageotropic curvature with slight swelling of stem, (3) an increased 

 swelling with further reduction of growth, (4) complete cessation of 

 growth in length with much swollen stem curved diageotropically, 

 (5) death of seedling. Richter(i5) has studied the structure of the swollen 

 zone of the stem and notes an abundant development of collenchyma 

 together with numerous cracks in the surface which are lined with 

 cork. 



