36 ZYGNEMATACEAE 



zygospores globose to ovoid, 25-35^ x 33-40 ju, somewhat compressed; 

 median spore wall yellow-brown, reticulate, with large irregular pits 

 7-12 )Li across. 



United States: Arkansas, Boston Mountains. 



59. Zygnema stellinum (Vaucher) Agardh 1824. Systema Al- 



garum, p. 77. 



Vegetative cells 28-38 /i x 27-ioo/A; conjugation scalariform, rarely 

 lateral between occasional pairs of cells; zygospores in one of the gam- 

 etangia; receptive gametangia inflated especially on the conjugating 

 side; zygospores ovoid, 30-42 /j. x 35-48 (-57)/^; median spore wall yel- 

 low-brown, thick, scrobiculate; pits 3-4 i^^ in diameter, 3-4 /a apart; 

 aplanospores common, usually cylindric, very rarely globose, the for- 

 mer filling the sporogenous cells, the latter occupying the middle of the 

 cells; spore walls similar to those of the zygospores. (Pi. I, Fig. 8; 

 PI. V, Fig. 16; and PL VI, Fig. i.) 



United States: Washington and California eastward, very common in 

 the central and eastern states. 



Canada; Greenland; Europe; Asia; South America; North Africa. 



60. Zygnema cruciatum (Vaucher) Agardh 1817. Synopsis Al- 



garum, p. 102. 



Vegetative cells 30-36 /it x 30-60 /x; conjugation scalariform; zygo- 

 spores in one of the gametangia; receptive gametangia cylindric or 

 enlarged; zygospores globose to ovoid, 30-38 ju. x 32-40 iu,; median spore 

 wall brown, scrobiculate; pits 1.5-2/A in diameter, 3-5 i"- apart; aplan- 

 ospores short, cylindric-ovoid, 30-35 /a x 30-60 /x, filling the vegetative 

 cells, otherwise similar to the zygospores. (PI. I, Fig. 9.) 



United States: Oklahoma; Iowa; Illinois; Massachusetts south to Mis- 

 sissippi and Florida. 



Reported from all the continents. 



61. Zygnema cylindrosporum Czurda 1932. Siisswasserfiora Mit- 



teleuropa. 9, p. 122, Fig. 126. 



Vegetative cells 31-36 m x 60-80 m; conjugation scalariform; zygo- 

 spores in one of the gametangia; receptive gametangia cylindric or 

 enlarged; zygospores short cylindric-ovoid to globose, 36-42 /x x 42-60 /a; 

 median spore wall yellow-brown, scrobiculate; pits about 1.5-2 /a in 

 diameter, 3-5/* apart; suture obliquely encircling the smaller circum- 

 ference of the spore. (PI. VI, Fig. 2.) 



Macedonia; northern India; South Africa. 



62. Zygnema bohemicum Czurda 1932. Susswasserfiora Mittcl- 



europa. 9, p. 124, Fig. 128. 



