(1) Icterogenin may be present in variable amounts in the leaves and inflorescence of Lippia rehmanni (pears) whereas only traces are to be found in the stem and root stele.
(2) There is a possible translocation of the toxic substance to the root cortex from the leaves, where presumably it is formed. The further possibility exists that the Icterogenin so stored in the root cortex may under certain specific conditions be translocated to the leaves of the plant. This point is receiving special attention in further work on this problem.
(3) The stage of growth does not appear to be of great importance as far as the toxicity of Lippia rehmanni (pears) is concerned. (4) Climatic conditions may to a large extent influence the synthesis and translocation within the plant tissues. (5) Pruning and cutting cause a marked increase in the concentration of Icterogenin in both the leaves and root cortex.
(6) From the work carried out on the plant Lippia rehmanni (pears) as described in this paper, the suggestion presents itself that the reciprocal translocation of toxic principles between the above ground and the subterranean portions of a plant may be factor of great significance in the determination of its toxicity. This point merits further investigation.