16 Pee OE DOICONTACEA'E 
original upper transverse wall of the primary cell, on the other. 
(Cf. Pl. L.XTI, figs. 606 and 612; Pl. EXITh figs, 616 and 623). 
Sexual reproduction of a rather advanced order has been 
observed in most species of the family. The position and 
relation of the oogonia and antheridia are used as classificatory 
items in all three genera. If oogonia and antheridia occur on 
the same filament the plant 1s monoecious (Pl. IX, fig. 69; 
Pl. XV, fig. 145); if on separate filaments, dzoecious (Pl. XX XIII, 
figs. 291 and 292). Oe. varians, Oe. trioicum, and perhaps a 
few others are both dioecious and monoecious. If dioecious, 
the male filaments may be about equal 1n size to the female, 
and the species is macrandrous (Pl. XXX, figs. 262 and 263). 
If the male plants are few-celled, much smaller (‘‘dwarf males”’ 
resulting from germinating androspores) and epiphytic on 
the female plant, the species is nannandrous (Pl. II, fig. 17; 
Pl. LII, fig. 494). If the dwarf males have arisen from the 
germination of androspores liberated from androsporangia 
occurring on the same filament with the oogonia, the alga is 
gynandrosporous (Pl. V, fig. 37; Pl. LIV, fig. 509; Pl. LXII, fig. 
606); if the androsporangia are formed on separate filaments 
from the oogonia, the alga is zdioandrosporous (Pl. VII, fig. 53; 
Pl. XLV, figs. 434 and 435). A few species among the nan- 
nandrous sections are both gynandrosporous and idioandros- 
porous. ‘The dwarf males form on the suffultory cell (Pl. VII, 
fig, 52: Pl. L, fig. 482), or on the oogonium (Pl V7 mesa; 
Pl. LIV, fig. 508), or rarely scattered on vegetative cells (Pl. 
XLV, fre8 455). 
In Oedogonium and Oedocladium a single division of a 
vegetative cell results in an oogonium and a suffultory (‘‘sup- 
porting’’) cell (Pl. LXIV, figs. 638-640). The latter (in 
Oedogonium) may by subsequent divisions form a series of 
oogonia (Pl. LIX, fig. 577). Flat discoid cells resulting from 
repeated transverse divisions of a vegetative cell are antheridia 
(in the monoecious and macrandrous species) and andro- 
sporangia (in the nannandrous species). No seriate oogonia 
are recorded for the species of Oedocladium. : 
In Bulbochaete oogonia are developed singly, never in 
series. An oogonium arises by a double division of a vegetative 
cell which thus results in two suffultory cells. After the first 
division the septum becomes fixed near the middle of the old 
sheath-like wall “‘so that the membrane of the upper segment 
is formed by a short cylindrical piece of the latter and above 
