ZYGOGONIUM. 225 



Received this plant repeatedly from the northern part of 

 Vermont, collected by Dr. F. Hosford; all the specimens 

 were in sterile condition, hence leaving- the generic position 

 somewhat in doubt. 



Ralfs and Hassall, of England, report this species having 

 the zygospores in the cells of the filaments; Kiitzing, of 

 Germany, on the contrary, reports it as having the spore 

 between the filaments in the canal of conjugation. While 

 there can be no doubt about its belonging to the Zygnemince, 

 it appears not decided whether it is constant as a Zygnema 

 or may be a Zygogonium. 



A remark by Ralfs on a character of the species under 

 consideration may be well to note: "In its usual state the 

 sheath is very conspicuous, and the dense endochrome so 

 fills the cells, that the plant looks like a Conferva, the con- 

 tinuity being interrupted merely at the dissepiments. When 

 about to conjugate the sheath has nearly, or altogether dis- 

 appeared, and the endochrome is collected into the stella?, 

 having the rest of the cell colorless." 



Plate CXLIV, fig. 9, part of vegetative filament as occur- 

 ring most frequently with wide sheath ; cells densely filled 

 with chlorophyl previous to its gathering into twin stellate 

 nuclei ; fig. 13, part of a fruiting filament more enlarged 

 tha^n fig. 9, may also represent an ideal fruiting filament of 

 var. craswm ; figs. 10, 11, 12, three parts, vegetative filaments 

 of var. crassum, in different stages of growth. 



Genus 73, ZYGOGONIUM, Kg. 



Filaments and arrangement of chlorophylous cell contents the 

 same as in Zygnema ; zygospore not in one or the other of the 

 conjugating cells, but in the bladder-like middle space between 

 the united pairing cells. Copulation scalariform, or lateral be- 

 tween cells of the same filament. 



Some modern authors have proposed classifying all of the fol- 

 lowing forms of this genus with Zygnema, using the argument 

 that the two modes of fruiting are not constant. Personal ob- 

 servations do not lead to the same conclusion ; deviations from 

 rule are rare, and then only with imperfectly developed fruit, 

 hence prefer the old division. 



ZYGOGONIUM PECTINATUM, Kg. 



Diameter of vegetative cells, 30-38 yw; cells 1-2-2 times 

 longer than broad, slightly constricted at the joints. Zygo- 

 spores globose, or broadly elliptic ; diameter about 50 yw 



