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ZY(;\KMATACEAE
PLATE I
Ri PRoiu cTivii Structlkls oh Zvgxemataceae
Fig. I.—Akinetes of Spirogyra jucrgensii from Crystal Springs, Mis-
sissippi, y\pril, 1925. The usual form of akinetes in this species is similar to
that of the vegetative cells. Fig. 2.—Akinetes of a Zygnema found at
Arcadia, Florida, February, 1931. Fig. 3.— Akinetes and zygospore of Spiro-
gyra jarlotvii from Topinohee, Michigan, July, 1934. Figs. 4-5.—Vegetative
cell and two aplanospores of Spirogyra wrightiana from Parahiba, Brazil,
July, 1934. Fig. 6.—Vegetative cell and two aplanospores of Zygnema frig-
idum from Smithville, Oklahoma, May, 1932. Fig. 7.—Aplanospores of
Spirogyra pratensis from Charleston, Illinois, May, 191 2. On two of the spo-
rangia figured are outgrowths that suggest the initials of conjugating tubes.
In many species these outgrowths are alternately or spirally arranged in suc-
cessive cells. When present they occur in only some of the sporangia.
Fig. 8.—Zygospores and parthenospores of Zygnema stcllnium from
Charleston, Illinois, May, 1912. This camera-lucida drawing also demon-
strates the distance between filaments through which conjugation may take
place. Fig. 9.—Aplanospores and zygospores of Z.ygnema cruciatam from
Coffeen, Illinois, May, 1915. Note that aplanospores occur in both male
and female filaments. Fig. 10.—Four zygospores of Mougeotia drouetii
from Fortaleza, Ceara, Brazil, October, 1935. This figure exemplifies sev-
eral species in which the cytoplasmic residues form a film enclosing the
zygospores.