320 Scientific Proceedings, Royal Dublin Society. 



No. 20 was brought from Canada to the Botanic Gardens of Trinity College, 

 Dublin, many years ago. It now grows luxuriantly in the shallower part of 

 a pond. Its leaves are 4-6 feet higli, and Mr. Dykes kindly identified it as 

 a typical I. psendacorm, which has gone wild in Canada. Nos. 17 and 18 are 

 also quite typical I. pseudaconis, and grow in marshy ground on the banks 

 of the Shannon in Co. Clare. With the exception of these two, all tlie 

 other pilants tested came from the College (hardens. The form 

 with variegated leaves, and the creamy variety, are much smaller 

 than the Canadian plant. The oream-ooloured flower, according to 

 Mr. Dykes, appears sometimes as a seedling from the normal yellow- 

 flowered plant. The plastids in it are of a much lighter colour than is usual. 

 Inspection of the table shows that the reactions are intense in the Canadian 

 and variegated leaved plants. The cream-coloured flower is No. 5 of Part I, 

 which is incorrectly named there, and is No. 31 of Part II. The Canadian 

 form is No 4 of Part I and No. 30 of Part II of this series. 



These reactions, obtained in 1913, agree well with those observed this year. 

 The Co. Clare plants are Nos. 28 and 29 in Part II, and the inhibitor appears 

 to be present in somewhat greater quantity than in the 1914 plants from the 

 same district. However, there is no doubt that there is a difference in the 

 peroxidase activity in these varieties of /. pseudacorutt. Next year, however, it 

 may be possible to examine a larger number of flowers of the same plant, and 

 so obtain more decisive evidence as to the existence of these physiologically 

 distinct varieties. 



It is frequently observed that the severed ends of standards and falls give 

 intense reactions witli both reagents, even in cases where the veins themselves 

 give little or no reaction. This has been attributed by Keeble and Armstrong 

 to the piroduction by the injured cells of wound peroxidase. It appears 

 quite probable, however, that the activity of the enzyme is in this case due to 

 the diffusion outwards of the inhibitor. For it has previously been shown 

 tliat treatment with hydrogen cyanide serves to remove it, and that it can be 

 dialysed away from sap pressed from the leaves, thus demonstrating tlie 

 presence of the enzyme where it was formerly believed to be absent. Solutions 

 of carbon dioxide were also found by Keeble and Armstrong to remove the 

 inldbitor. Since both hydrogen cyanide and carbon dioxide render the proto- 

 plasm more permeable without coagulating it to the same degree as do 

 alcoholic solutions, there seems to be reason for supposing that it is to this 

 physical action, rather than to a chemical change, that the removal of the 

 inhibitor is due. Por diffusion is now unchecked. 



