GONATONEMA. 233 



Genus 77, PLAGIOSPERMUM, Cleve. 



Cells cylindrical, united into filaments ; cell contents similar 

 to other Mesocarpince. Spores spherical or broadly oval in one 

 of the conjugated cells. The spore-bearing cell somewhat in- 

 flated and shortened by distinct and thickened, suture-like, par- 

 tition walls. 



PLAGIOSPERMUM TENUE, Cleve; var. MINOR, Wolle. 



Diameter of vegetative filaments, 17-18 }J. ; cells 4-8 times 

 longer than broad. Spores spherical, 2-2 times more in 

 diameter than the filaments. Spores dark green to brown 

 or red. 



The filaments of the typical form found in Sweden and 

 described by Cleve, measure 25-30 //, and cells 8-16 times 

 longer than broad. 



Shallow pools, Bethlehem, Pennsylvania, and Florida. 

 Plate CXLYIII, figs. 11-15, fruiting filaments ; the same 

 are also found in series of fruiting cells on the same filaments. 



Genus 78, GONATONEMA, Wittr. 



Cells elongated, cylindrical, united into filaments with axile 

 plates of chlorophyl. Agamospores produced without conjuga- 

 tion, formed by biseptation of the mother cells, which latter are 

 often bent angularly, and alternately, at the point of fructi- 

 fication. 



GONATONEMA" VENTRICOSUM, Wittr. 



Diameter of vegetative filaments, 5-6 fj. ; cells 8-12 times 

 longer than broad, somewhat geniculately bent ; spore- 

 bearing cells inflated ; spores spherical or broadly oval. 



Prof. Wittrock, of the Academy of Science, Stockholm, 

 made a thorough investigation of the spore-formation of the 

 Mesocarpece and especially on the new genus Gonatonema. 

 The paper is too long for transfer to these pages ; a few words 

 may be quoted: "It appears that the spores are always 

 formed without a preceding act of conjugation. The spore 

 formation, therefore, may be regarded as neutral, or we may 

 assume that, as in exceptional cases, spores may be formed 

 by the instrumentality of a single cell ; in this case the ex- 

 ception has become the rule, and the spores would then be 

 regarded as parthenospores, and not as agamospores. " 



"Because this plant differs in such an essential respect in 

 the spore from the other Mesocarpece, I have thought fit to 

 form a new genus for it, to which I have given the name of 

 Gonatonema, meaning geniculate filament." 



