NON-FILAMENTOUS AQUATIC FUNGI
85
cell have gone by the board, we are left with a terminal, thick-walled,
pigmented, dormant, resistant sporangium, borne upon an empty rootlike cell. Its subsequent fate now depends upon the environment in
which it finds itself ; it may germinate immediately, or it may remain in
its state of suspended animation for many years.
G. Differentiation and Discharge of Zoospores
In this final section, we propose to deal briefly with the process of
spore cleavage. Unfortunately, with the exception of some elegant
cytological investigations on the genesis of gametes in Allomyces (Turian,
1955, 1956, 1958; Blondel and Turian, 1960), experimental assaults on
this challenging problem have been rare. Consequently, our discussion
will place its emphasis on the potential import of spore differentiation
for studies of experimental morphology.
The cleavage of a multinucleate sporangium into many uninucleate
spores must involve an extensive intracellular reorganization of both
structure and function. In B. emersonii, for example, the largest and
most sudden shifts in metabolism occur during germination of the RS
cell (Cantino, 1961b). The process starts with a single, quiescent, thickwalled multinucleate cell possessing very low respiratory and enzymatic
activity; it ends in the manufacture of some 6,500 uniflagellate spores
which contain unique and highly organized structures such as nuclear
caps and side bodies, display very high respiratory rates and many
active enzymes, and have sufficient motive power to briskly dart about
for long periods of time. Germination of the OC cell is somewhat less
spectacular, in part because a stage of dormancy does not intervene in
the transition from active growth to spore formation.
RS cells are induced to germinate when they are immersed in water ; a
distinct lag of 2 or 3 hours is involved. The OC cell, on the other hand,
discharges spores almost immediately after it reaches maturity, whether
or not it is submerged in water (although precocious cleavage of zoospores does result when the growth medium is replaced with water). The
difference in the time requirements for discharge of spores from the two
cell types reflects differences in their physical and metabolic states; i.e.,
dormancy vs. active growth. Germination of the RS cell is a two-stage
process (Cantino, 1951); the first stage results in cracking of the thick,
chitinous wall along visible pre-formed zones of weakness ; the second, in
the discharge of spores via a pore formed by deliquescence of a protruberant papillum. The two stages are distinguished by the facts that
(a) cracking of the RS cell and subsequent liberation of its spores can be
differentially inhibited by manipulation of temperature, metabolic
inhibitors, and ionic environment; and (b) differentiation of motile
spores without concomitant cracking of the wall has been detected in
85
cell have gone by the board, we are left with a terminal, thick-walled,
pigmented, dormant, resistant sporangium, borne upon an empty rootlike cell. Its subsequent fate now depends upon the environment in
which it finds itself ; it may germinate immediately, or it may remain in
its state of suspended animation for many years.
G. Differentiation and Discharge of Zoospores
In this final section, we propose to deal briefly with the process of
spore cleavage. Unfortunately, with the exception of some elegant
cytological investigations on the genesis of gametes in Allomyces (Turian,
1955, 1956, 1958; Blondel and Turian, 1960), experimental assaults on
this challenging problem have been rare. Consequently, our discussion
will place its emphasis on the potential import of spore differentiation
for studies of experimental morphology.
The cleavage of a multinucleate sporangium into many uninucleate
spores must involve an extensive intracellular reorganization of both
structure and function. In B. emersonii, for example, the largest and
most sudden shifts in metabolism occur during germination of the RS
cell (Cantino, 1961b). The process starts with a single, quiescent, thickwalled multinucleate cell possessing very low respiratory and enzymatic
activity; it ends in the manufacture of some 6,500 uniflagellate spores
which contain unique and highly organized structures such as nuclear
caps and side bodies, display very high respiratory rates and many
active enzymes, and have sufficient motive power to briskly dart about
for long periods of time. Germination of the OC cell is somewhat less
spectacular, in part because a stage of dormancy does not intervene in
the transition from active growth to spore formation.
RS cells are induced to germinate when they are immersed in water ; a
distinct lag of 2 or 3 hours is involved. The OC cell, on the other hand,
discharges spores almost immediately after it reaches maturity, whether
or not it is submerged in water (although precocious cleavage of zoospores does result when the growth medium is replaced with water). The
difference in the time requirements for discharge of spores from the two
cell types reflects differences in their physical and metabolic states; i.e.,
dormancy vs. active growth. Germination of the RS cell is a two-stage
process (Cantino, 1951); the first stage results in cracking of the thick,
chitinous wall along visible pre-formed zones of weakness ; the second, in
the discharge of spores via a pore formed by deliquescence of a protruberant papillum. The two stages are distinguished by the facts that
(a) cracking of the RS cell and subsequent liberation of its spores can be
differentially inhibited by manipulation of temperature, metabolic
inhibitors, and ionic environment; and (b) differentiation of motile
spores without concomitant cracking of the wall has been detected in