4
F. B. SHORLAND
has been shown that in some plants, such as flax (linseed), the seed
oils are fairly characteristic of the species though occasional variations
occur with different varieties of seed and in different climatic conditions. However, variants from the normal or usual type of fat have
been found in seed fats. Although safflower (Carthamus
tintforius)
seed oil normally has an iodine value of about 140-150 and contains
about 10% saturated acids with 20% oleic and 70% linoleic acid, Horowitz
and Winter (4) found two individual specimens among a large number
of plants whose seed oils had iodine values of only 100 and 105. From
these specimens a variant has been bred whose seed oil has an iodine
value ranging from 91 to 101. Moreover, the fatty acid composition is
changed from that of the normal seed oil and consists of saturated
acids, 4-8%; oleic acid, 74-79%; and linoleic acid, 11-19%. The elaboration of different fatty acids within a given species of plant has not yet
been observed, but the possibility cannot be overlooked in the light of
observations on other constituents. Different strains of the same organism
may elaborate different types of fatty acids. Thus the physiologically
active α,β-unsaturated C 27 -phthienoic acid is present in virulent strains
of the tubercle bacillus but absent from the nonvirulent strains, which
also show other differences in the composition of the higher branchedchain fatty acids (5).
While admitting broad differences between species in different parts
of the phylogenetic scale, we have therefore to accept the possibility of
occasional considerable variation in fatty acid composition between
individuals of the same species and even the occurrence of specific
fatty acids in one individual and their absence in another. Furthermore, studies on the occurrence of essential oils and alkaloids show
that species which are adjudged to be the same on morphological
grounds may elaborate different substances. A striking illustration of
this is afforded by the work of Penfold and Morrison (6). This shows
that the composition of the essential oil of eucalypts cannot be used, as
earlier supposed by Baker and Smith (7), as an unequivocal guide to
botanical classification. The first evidence of chemical variation was
obtained in 1924 from specimens of Eucalyptus dives, which, though
morphologically identical, elaborated in their leaves entirely different
types of essential oils. Penfold and Morrison (8) distinguished three
physiological forms within this species, each of which propagates its
own form with the same characteristic essential oil. The variations in
chemical composition are not altered by the environment but are inherent in the physiological form.
In the alkaloid field, examples of variations within a given species
include the elaboration of hyoscine as the main alkaloidal constituent
F. B. SHORLAND
has been shown that in some plants, such as flax (linseed), the seed
oils are fairly characteristic of the species though occasional variations
occur with different varieties of seed and in different climatic conditions. However, variants from the normal or usual type of fat have
been found in seed fats. Although safflower (Carthamus
tintforius)
seed oil normally has an iodine value of about 140-150 and contains
about 10% saturated acids with 20% oleic and 70% linoleic acid, Horowitz
and Winter (4) found two individual specimens among a large number
of plants whose seed oils had iodine values of only 100 and 105. From
these specimens a variant has been bred whose seed oil has an iodine
value ranging from 91 to 101. Moreover, the fatty acid composition is
changed from that of the normal seed oil and consists of saturated
acids, 4-8%; oleic acid, 74-79%; and linoleic acid, 11-19%. The elaboration of different fatty acids within a given species of plant has not yet
been observed, but the possibility cannot be overlooked in the light of
observations on other constituents. Different strains of the same organism
may elaborate different types of fatty acids. Thus the physiologically
active α,β-unsaturated C 27 -phthienoic acid is present in virulent strains
of the tubercle bacillus but absent from the nonvirulent strains, which
also show other differences in the composition of the higher branchedchain fatty acids (5).
While admitting broad differences between species in different parts
of the phylogenetic scale, we have therefore to accept the possibility of
occasional considerable variation in fatty acid composition between
individuals of the same species and even the occurrence of specific
fatty acids in one individual and their absence in another. Furthermore, studies on the occurrence of essential oils and alkaloids show
that species which are adjudged to be the same on morphological
grounds may elaborate different substances. A striking illustration of
this is afforded by the work of Penfold and Morrison (6). This shows
that the composition of the essential oil of eucalypts cannot be used, as
earlier supposed by Baker and Smith (7), as an unequivocal guide to
botanical classification. The first evidence of chemical variation was
obtained in 1924 from specimens of Eucalyptus dives, which, though
morphologically identical, elaborated in their leaves entirely different
types of essential oils. Penfold and Morrison (8) distinguished three
physiological forms within this species, each of which propagates its
own form with the same characteristic essential oil. The variations in
chemical composition are not altered by the environment but are inherent in the physiological form.
In the alkaloid field, examples of variations within a given species
include the elaboration of hyoscine as the main alkaloidal constituent