For many years experimental grafting of alkaloid-forming plants on non-alkaloid-bearing stocks and vice versa has been carried out in several laboratories (Hieke, 1942;Dawson, 1942Dawson, , 1944James, 1944James, , 1945Cromwell, 1943), and considerable evidence has accumulated to suggest that the main seat of alkaloid synthesis in the plants normally forming mydriatic alkaloids is in their root systems (Dawson, 1948). In every case this work involved the grafting of a member to whom mydriatic alkaloids are foreign, and the results showed simply presence or absence of alkaloids. Recently, methods have been described by which the alkaloids hyoscyamine (including atropine) and hyoscine can be estimated separately in mixtures and so the ratio of the alkaloids in the plant can be determined. Trautner & Roberts (1948) described a method for the estimation of these alkaloids, a separation of the mixed bases being first achieved by adsorption chromatography, using activated silica, followed by titration. The method fails if the hyoscine proportion is less than 10% of the total; hence, while applicable to extracts from Duboisia species and many species of Datura (such as D. innoxia)*, it is unsuitable for extracts from Atropa belladonna. Evans & Partridge (1948) have more recently described a method using partition chromatography which can be used for extracts containing lower proportions of hyoscine. In the present investigation their work has been developed so that the method can be used to estimate these alkaloids in actual plant extracts; this made it possible to determine the hyoscine/hyoscyamine ratio in the plants, and it became clear that in Datura innoxia and Atropa belladonna, characteristic and very different ratios were normally developed. This suggested that reciprocal grafts of these two species in which both alkaloids are normally formed, but in very different proportions, might produce further and rather more elegant experimental evidence than was obtainable in the earlier work involving non-alkaloidal plants. A series of reciprocal grafts was made, therefore, and stock and scion dried and analysed separately as described below.
METHODSThe grafts were all made as 'slip grafts'; a slip with terminal bud and two or three leaves was taken from a young, rapidly growing plant, the stem was trimmed to the shape of a narrow wedge and inserted in a slit made in a young stock plant. The slit was made below a leaf in the soft part of a growing stem. The whole was then bound tightly with raffia, and kept in a moist atmosphere. After 10 days or a fortnight the shoot of the stock • The name Datura innoxia is used in this paper for the plant commonly known as D. metel, as it appears from the work of Timmerman (1927) that the former name is correct.