gallinarum eggs contained in either feces or soil. Histomonas meleagridis also can
exist as larvae in earthworms, which presents another feeding related route of
acquisition by birds. Pierre-Joseph van Beneden often is credited with having
introduced the terms mutualism and commensalism, although I found first listing
of these terms in a publication by Bernhard Frank (1877).
de Bary mentioned epiphytic plants such as orchids, and their host plants, when
considering mutualistic and commensal relationships. de Bary suggested that the
epiphytes could be considered commensuals of the host plants even though the
epiphytes are chlorophyll-containing plants and therefore should be able to satisfy
their own energetic needs. By my interpretation, his words were: “At the most, one
could still call them commensals of the latter; but this designation applies to all
non-parasitic plants that live in the same place [i.e., on either a tree or some other
physically supportive host plant]”.
de Bary then mentioned the symbiotic association between Azolla and a cyanobacterium, Trichormus azollae (previously named Anabaena azollae).
Although the cyanobacterium can exist on it’s own, that cyanobacteria typically
is found within cavities inside the leaves of Azolla. In this classically symbiotic
relationship, the cyanobacterium receives carbon compounds from the Azolla plant
in exchange for supplying fixed nitrogen to the Azolla. We humans traditionally have
used that particular relationship in agriculture by having the growth of Azolla in the
water of rice paddies provide a source of fixed nitrogen for the rice plants.
de Bary also mentioned the symbiotic association between Nostoc, in reference to
a genus of cyanobacteria which we now know by the name Anabaena cycadae, and
its host plants of the order Cycadales. Anabaena cycadae invades the cycad plant
structures termed coralloid roots, whereafter the Anabaena cycadae then resides and
fixes nitrogen within the middle cortex of those coralloid roots.
de Bary additionally mentioned lichens, which are a symbiotic association
between a fungus and either an algae or cyanobacterium “For most lichens, however,
things are very different [for] ... the algae [which] can exist independently. Not only
can they be artificially isolated and they can continue to vigorously vegetate and
reproduce on their own, but the algae forms can also be found spontaneously in
many cases growing on their own without being part of a lichen body.” and “The
lichen fungus behaves the other way round. As has already been said, he is incapable
of independent training without the algae and quickly dies if he does not find it,
because he depends on her carbonic acid [I did not quite understand that, because it is
the fungal component rather than the algae which produces the carbonic acid]
assimilation to obtain the building materials for his growth. But it [the fungal
component of the lichen] does not simply settle on or in the algae, but grows around
it, absorbs it into its own body and then, with most lichens, in turn increases its mass
so enormously that it is by far the main component of the common [whereas] the
algae form a small fraction, or much less. After the two codependents have divided,
the mushroom [fungal] owner, host, is the algae guest. However, the landlord is
dependent on the guest to live—which also happens otherwise. Accordingly, the
guest is treated with the utmost care: not only [should] his growth not be impaired,
but, as we will see later, it is often prominently promoted in comparison with the
218
C. J. Hurst
exist as larvae in earthworms, which presents another feeding related route of
acquisition by birds. Pierre-Joseph van Beneden often is credited with having
introduced the terms mutualism and commensalism, although I found first listing
of these terms in a publication by Bernhard Frank (1877).
de Bary mentioned epiphytic plants such as orchids, and their host plants, when
considering mutualistic and commensal relationships. de Bary suggested that the
epiphytes could be considered commensuals of the host plants even though the
epiphytes are chlorophyll-containing plants and therefore should be able to satisfy
their own energetic needs. By my interpretation, his words were: “At the most, one
could still call them commensals of the latter; but this designation applies to all
non-parasitic plants that live in the same place [i.e., on either a tree or some other
physically supportive host plant]”.
de Bary then mentioned the symbiotic association between Azolla and a cyanobacterium, Trichormus azollae (previously named Anabaena azollae).
Although the cyanobacterium can exist on it’s own, that cyanobacteria typically
is found within cavities inside the leaves of Azolla. In this classically symbiotic
relationship, the cyanobacterium receives carbon compounds from the Azolla plant
in exchange for supplying fixed nitrogen to the Azolla. We humans traditionally have
used that particular relationship in agriculture by having the growth of Azolla in the
water of rice paddies provide a source of fixed nitrogen for the rice plants.
de Bary also mentioned the symbiotic association between Nostoc, in reference to
a genus of cyanobacteria which we now know by the name Anabaena cycadae, and
its host plants of the order Cycadales. Anabaena cycadae invades the cycad plant
structures termed coralloid roots, whereafter the Anabaena cycadae then resides and
fixes nitrogen within the middle cortex of those coralloid roots.
de Bary additionally mentioned lichens, which are a symbiotic association
between a fungus and either an algae or cyanobacterium “For most lichens, however,
things are very different [for] ... the algae [which] can exist independently. Not only
can they be artificially isolated and they can continue to vigorously vegetate and
reproduce on their own, but the algae forms can also be found spontaneously in
many cases growing on their own without being part of a lichen body.” and “The
lichen fungus behaves the other way round. As has already been said, he is incapable
of independent training without the algae and quickly dies if he does not find it,
because he depends on her carbonic acid [I did not quite understand that, because it is
the fungal component rather than the algae which produces the carbonic acid]
assimilation to obtain the building materials for his growth. But it [the fungal
component of the lichen] does not simply settle on or in the algae, but grows around
it, absorbs it into its own body and then, with most lichens, in turn increases its mass
so enormously that it is by far the main component of the common [whereas] the
algae form a small fraction, or much less. After the two codependents have divided,
the mushroom [fungal] owner, host, is the algae guest. However, the landlord is
dependent on the guest to live—which also happens otherwise. Accordingly, the
guest is treated with the utmost care: not only [should] his growth not be impaired,
but, as we will see later, it is often prominently promoted in comparison with the
218
C. J. Hurst