A, Portion of a young aecidium.
st, Sterile cell.
a, Fertile cells; at a2 the passage of a nucleus from the adjoining
cell is seen.
B, Formation of the first spore-mother-cell (sm), from the basal
cell (a) of one of the rows of spores.
C, A further stage in which from sm1 the first aecidiospore (a) and
the intercalary cell (z) have arisen.
sm2, The second spore-mother-cell.