ments in aboriginal religions (Schultes 1969a; Schultes and 
Hofmann, 1979). 
Scientific interest in hallucinogenic agents remains high in the 
hope of finding potentially valuable drugs for use in experi- 
mental or even therapeutic psychiatry and also because they 
might prove useful as tools to study biochemical origins of 
mental abnormalities. 
While psychoactive species are widely scattered throughout 
the plant world, they appear to be more or less concentrated 
amongst the fungi and the angiosperms. The bacteria, algae, 
lichens, bryophytes, ferns and gymnosperms seem to be notably 
poor or lacking in species with hallucinogenic properties 
(Schultes 1969c, 1969d, 1970a, 1981: Schultes and Hofmann 
1980). These hallucinogenic properties can be ascribed, likewise, 
to only a few kinds of organic constituents, which may be conve- 
niently divided into two broad groups: nitrogenous and non- 
nitrogenous compounds (Der Marderosian 1967a; Farnsworth 
1968, 1969; Schultes 1970c; Schultes and Hofmann 1973 and 
1980). See Figure | for the basic chemical skeletons of these 
compounds. 
The nitrogenous compounds play by far the greater role and 
comprise, for the most part, alkaloids or related substances, the 
majority of which are or may be biogenetically derived from the 
indolic amino acid tryptophan. They may be classified into the 
following groups: 1. B-carbolines; 2. ergolines; 3. indoles; 4. 
isoxazoles; 5. B-phenylethylamines; 6. quinolizidines; 7. tro- 
panes; and 8. tryptamines. Non-nitrogenous compounds, which 
are the active principles in at least two well known hallucino- 
gens, include monoterpenoid chromenes and phenylpropenes. 
In the study of hallucinogenic plants, two considerations must 
be borne in mind. One consideration reminds us that, although 
some of these psychoactive plants are used in primitive societies, 
their active chemical principles are as yet not known. The other 
emphasizes that man undoubtedly has utilized only a few of the 
species that actually do possess hallucinogenic principles. We 
are, as yet, far from knowing how many plants are endowed with 
psychotomimetic constituents, but there are certainly many 
more than the few purposefully employed by man as hallu- 
cinogens. 
125 
