16. Brown, Jr. R. M. and R. Wilson. 1968.
Ultrastructure of the lichen Physcia aipolia (Ehrh) NYL.
J. Phycol. 4:230-240.
The ultrastructure of the lichen Physcia
aipolia was studied in the desiccated and hydrated states.
No significant structural variation between these 2 states was
noted for the fungus. The fungus contains unusual ellipsoidal
structures heretofore unobserved. Their possible role in the formation
of membrane is discussed. The plasmalemma of the fungus is convoluted
while that of the alga is smooth. The convoluted projections
have a "double-unit membrane" structure similar to fingerlike
projections of the ellipsoidal bodies. With OsO4 fixation
crystals are preserved, enclosed in unit membrane sacs which extend
to the convoluted surface. The pyrenoid of the associated alga
does not produce starch in the desiccated condition, and electron-dense
granules are present in the matrix associated with chloroplast
lamellae which enter this area. In the hydrated condition, the
alga contains abundant starch in the pyrenoid region, and the
electron-dense granules are displaced to the periphery of the
pyrenoid starch. Mitochondria, endoplasmic reticulum, and ribosomes
are not clearly defined in the desiccated state while they are
more so in the hydrated condition. Golgi bodies were not observed
in either lichen component. Finally, no fine structural basis
for indicating an exchange of materials between the alga and fungus
was observed except, possibly, the convoluted plasmalemma of the