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EDGAR NELSON TRANSEAU 
Zygnema decussatum (Vauch.) no v. comb. 
Synonyms: Zygnema pectinatum (Vauch.) Ag. var. decussatum 
(Vauch.) Kirch., Zygogonium decussatum (Vauch.) Kuetzing, Tyn- 
daridea decussata Hassall, Conjugata decussata Vaucher. 
Both Z. pectinatum (Vauch.) Ag. and the so-called variety decus- 
satum (Vauch.) Kirch, are common in the ponds, pools, and ditches of 
eastern Illinois. They have little in common except that both form 
scrobiculate spores in the conjugating tube. They sorhetimes occur 
in the same ponds but more frequently not. The species in the 
permanent ponds is essentially a perennial, while the variety in all 
stations is a late spring annual. Z. decussatum forms vivid green 
flocculi on the surface of ponds in which it occurs. Z. pectinatum is 
usually submerged and possesses a thick mucilaginous outer wall. 
The cells of the former are 3-5 times as long as the diameter, of the 
latter from 1-3 times. The dimensions of the former throughout are 
but little more than half those of the latter. In view of all these 
differences it seems best to separate the variety and give it specific 
rank. 
Spirogyra Narcissiana nov. sp. 
Filamentis plerumque sparsis; cellulis vegetativis 12-14 latis, 
diametro 15-30-plo longioribus; chromatophoris singulis, gracilis, 
laxi anfractibus 2-5; dissepimenta cellularum semireplicata ; cellulis 
fructiferis valde medio inflatis (ventricosis vel quasi quadraticis), 
25-33 M latis, haud abbreviatis; aplanosporis ellipticis vel ovoideis, 
maturitate flavescentibus, 23-30 ^ latis, 50-120 ^ longis. 
Filaments usually scattered; vegetative cells 12-14 M X 200-400 11, 
one chromatophore, slender, making 2-5 turns in the cell; dissepiments 
semireplicate (i. e. the fold in wall extends only through an arc of 180° 
instead of 360°, and fold in the wall of the adjoining cell alternates 
with it) ; fertile cell much inflated toward the middle, either rounded 
or quadrate in outline, 25-33 in diameter, not shortened; aplano- 
spores elliptical to ovoid, 23-30 ix X 50-120 ix, yellow at maturity. 
This species is intermediate between the two divisions of the genus : 
Conjugata (Vauch.) Hansg. and Salmacis (Bory.) Hansg. This fact 
together with its aplanosporic habit of reproduction, and the quadrate 
form of the inflation of the fertile cells, make it a species of peculiar 
interest. Thus far it has been recorded from the dam at Urban Park, 
Charleston, 111., during September and October, 191 2. Type in herb. 
E. N. T. Collections No. 1682, 1663. Plate XXV, figures 4-8. 
