The identification of the 'apparent vitamin C' of the walnut (Juglans regia) with hydrojuglone glucoside.

use in the oxidation-reductions systems associated with increased cell metabolism. Owing to this growth, the concentration levels fall sufficiently to allow translocation of this substance from other parts of the plant to these rapidly growing centres, so that the amount actually present increases. This increase obliterates the losses that should be detected were the glucoside utilized in the formation ofnew tissues, save in the endocarp where there is a falling off in the amount present with increased lignification of the shell. In the previous year's growth the glucoside is also found in the young phloem immediately external to the cambium ring, where it may be used in new tissue formation. A third possible use is found in the fact that quinones of the juglone type are toxic to the lower forms of plant life such as moulds, fungi and bacteria. The highest concentrations ofthe glucoside occur in tissues concerned with the reproductive cycle, and after fertilization of the flower and the maturation of the fruit are accomplished, these huge amounts are discarded in the male catkins and the husks. From this it would appear that it is used as a protective agent to ensure the success of these processes. The large amounts in the husk persist until the lignification of the shell is complete, thus preventing bacterial or other penetration to the ripening seed. Should the seed be attacked, then large amounts of the hydrojuglone glucoside infiltrate to prevent further damage. In a similar manner the vegetative buds are protected to ensure the appearance of the shoots for the following year. This toxic action was also observed by Reinking (1943) in that many annuals will not grow in the vicinity ofwalnut trees. None of these suggestions for the role of the glucoside takes into account the large amounts of ascorbic acid which are known to be present in the young fruits. It is possible that there is some definite interaction of these two substances depending upon the differences in electrode potentials. This can only be determined by a further study ofthe occurrence of the ascorbic acid, which work is still in progress.