55 



in the soil, since the conditions of the drain tile stimulate root 

 development very materially. However, the root system of any 

 tree or shrub is far in excess in length and area of what the lay- 

 man imagines. The profuse growth of roots in water is also 

 seen in cases where old wells become filled with root growth, 

 but the pear tree root in question is one of the best examples 

 which has ever come to our notice of root development in drain 

 tile. 



Massachusetts Agricultural Experiment Station, 

 Amherst, Massachusetts. 



THE NATURE AND FUNCTION OF THE PLANT 

 OXIDASES 



By Ernest D. Clark] 

 (Continued from February Torreya) 



Peroxidase 

 Besides the laccase and tyrosinase which we have been con- 

 sidering, there are other oxidizing enzymes which are not specific 

 like the two mentioned. They act only in the presence of hydro- 

 gen peroxide, and therefore are called peroxidases. These en- 

 zymes have also been called "indirect oxidases" in distinction 

 from those substances (Bach's oxygenases) which show their 

 activity without the addition of peroxide as in the case of tyro- 

 sinase, etc. In 1903, Bach and Chodat^^ discovered that by 

 fractional precipitation of aqueous extracts of Lactarius vellereus, 

 they were able to obtain two precipitates of very different prop- 

 erties. The fraction insoluble in 40 per cent, alcohol proved to 

 be a direct oxidase, while the other fraction, soluble in 40 per 

 cent, alcohol, but insoluble in 95 per cent, alcohol, had no direct 

 oxidizing properties. With hydrogen peroxide and other perox- 

 ides, however, the second fraction showed strikingly peroxidase 

 properties. Moreover, the peroxidase fraction, when allowed to 

 act with the direct oxidase fraction, showed all the properties of 



1^ Bach and Chodat. Title of series is: Untersuchungen iiber die Rolle der Per- 

 oxyde in der Chemie der lebenden Zellen; V. Zerlegung der sogenannte Oxydasen 

 in Oxygenasen und Peroxydasen. Ber. Chem. Gesell. 36: 606. 1903. 



