NON-FILAMENTOUS AQUATIC FUNGI
37
stages of ontogeny further reveals the potential utility of this organism
for direct microscopic observations and cytochemical studies throughout
its development.
On the other hand, it also follows that if the crowbars of the biochemist, for example, are ultimately to be brought to bear upon
Rhizidiomyces,
then cultures synchronized on a much more massive
scale than is possible on cover-slips will have to be obtained. To try to
purify some crucial enzyme 50-fold, and to have to lose 90% of it in the
process, would be manifestly difficult if not impossible with several
hundred tiny plants in place of several hundred rats or cakes of baker's
yeast. It seems reasonable to assume that large-scale cultures can be
obtained through the use of much more massive spore suspensions (by
simply flooding larger populations of the parent plants, as has been done
with Blastocladiella; see later). And if, in particular, spores can be made
to discharge synchronously (this appears to be a major hurdle; Fuller,
1962) in large quantity, then Fuller's Rhizidiomyces will provide a lovely
system for studying the events involved in differentiation, completion
of a life-history, and the start of a new generation—formation of the
discharge tube and vesicle, enlargement of the uncleaved protoplast,
and its final segmentation into spores, all of which can apparently be
made to happen in something more than half an hour. With the background information already available on the nature of the wall material
in this fungus (Fuller, 1960; Fuller and Barshad, 1960), there is no doubt
that Rhizidiomyces will get well-deserved attention in the future.
B. Rhizophlyctis rosea
Rhizophlyctis
rosea is a ubiquitous representative of a large and
relatively unexplored group of simple, non-filamentous chytrids ; it can
be isolated with ease. After the small, posteriorly-uniflagellate zoospore
loses its flagellum, it gradually enlarges with concomitant production of
an extensive, branched rhizoidal system. The mature plant is nearly
spherical; several peg-like discharge papillae are scattered over the
upper hemisphere, and many rhizoids are attached to the lower one.
On approaching maturity, the organism rapidly lays down the carotene
which produces the characteristic orange pigmentation of the species.
Finally, it discharges large numbers of motile spores which immediately
and rapidly swim away to begin the process anew.
Surprisingly little work has been done with this organism, which is so
easily handled and holds such great promise for future study. Many
years ago (Couch, 1939), heterothallism was reported to occur in
Rhizophlyctis,
but whether or not it does indeed display sexuality
remains a moot point. However, its evolutionary success, attested to by
its common occurrence and world-wide distribution, may imply that sex
37
stages of ontogeny further reveals the potential utility of this organism
for direct microscopic observations and cytochemical studies throughout
its development.
On the other hand, it also follows that if the crowbars of the biochemist, for example, are ultimately to be brought to bear upon
Rhizidiomyces,
then cultures synchronized on a much more massive
scale than is possible on cover-slips will have to be obtained. To try to
purify some crucial enzyme 50-fold, and to have to lose 90% of it in the
process, would be manifestly difficult if not impossible with several
hundred tiny plants in place of several hundred rats or cakes of baker's
yeast. It seems reasonable to assume that large-scale cultures can be
obtained through the use of much more massive spore suspensions (by
simply flooding larger populations of the parent plants, as has been done
with Blastocladiella; see later). And if, in particular, spores can be made
to discharge synchronously (this appears to be a major hurdle; Fuller,
1962) in large quantity, then Fuller's Rhizidiomyces will provide a lovely
system for studying the events involved in differentiation, completion
of a life-history, and the start of a new generation—formation of the
discharge tube and vesicle, enlargement of the uncleaved protoplast,
and its final segmentation into spores, all of which can apparently be
made to happen in something more than half an hour. With the background information already available on the nature of the wall material
in this fungus (Fuller, 1960; Fuller and Barshad, 1960), there is no doubt
that Rhizidiomyces will get well-deserved attention in the future.
B. Rhizophlyctis rosea
Rhizophlyctis
rosea is a ubiquitous representative of a large and
relatively unexplored group of simple, non-filamentous chytrids ; it can
be isolated with ease. After the small, posteriorly-uniflagellate zoospore
loses its flagellum, it gradually enlarges with concomitant production of
an extensive, branched rhizoidal system. The mature plant is nearly
spherical; several peg-like discharge papillae are scattered over the
upper hemisphere, and many rhizoids are attached to the lower one.
On approaching maturity, the organism rapidly lays down the carotene
which produces the characteristic orange pigmentation of the species.
Finally, it discharges large numbers of motile spores which immediately
and rapidly swim away to begin the process anew.
Surprisingly little work has been done with this organism, which is so
easily handled and holds such great promise for future study. Many
years ago (Couch, 1939), heterothallism was reported to occur in
Rhizophlyctis,
but whether or not it does indeed display sexuality
remains a moot point. However, its evolutionary success, attested to by
its common occurrence and world-wide distribution, may imply that sex