52 



THE AMERICAN MONTHLY 



[March, 



zygospore into 3 or 5 parts, a central 

 green spherical mass, with 2 or 4 

 outer cells, which are the remains of 

 the original conjugating cells, soon 

 to disappear. The result of this 

 conjugation, therefore, is a very low 

 form of sporocarpium, and the re- 

 sulting, germinating spore is not a 

 zygospore but a carpospore.] 



a. Zygnemin.^. Sub-group i. 



Syitopsis of Genera. 



Cells with spiral green bands. 



Spzrog-yra., 82. 



Cells with straight or slightly spiral 



green bands. Sirogonium., 83. 



Cells with two green stellate 



masses. Zyg-nema^ 84. 



Cell contents irregular ; cell-walls 



thick, or many-layered. 



Zygogotihim^ 85. 



Cells with single, axial green band. 



Mongeotia, 86. 



82. Genvis Spirogyra Link. 

 Cells with one or more spiral 



bands of chlorophyll. 



Copulation ladder-like {Spi?'ogy>'a 

 Kiitzing) or lateral {Rhynchonetna 

 Kiitzing) . Zygospores smooth, 

 within one of the copulating cells. 



83. Genus Sirogofiiiim Kiitzing. 

 Cells with several straight or 



slightly spiral chlorophyll bands. 



Copulation geniculate ; copulating 

 cells of different forms and sizes, the 

 receiving cells (female) elongated, 

 the others (male) short-cylindric. 

 Zygospore formed within the cells. 



84. Genus Zygnema Kiitzing. 

 Cells with two radiating stellate 



green bodies. 



Copulation ladder-like or lateral. 

 Zygospore within one of the cells, as 

 in Spirogyra ; membrane smooth or 

 rough. 



85. Genus Zygogoniitm Kiitzing. 

 Cells cylindrical or barrel-shaped, 



with thick, often many-layered cell- 

 walls. On either side, near the 

 middle, an irregular chlorophyll 

 body with a starch-grain, both often 

 running together into an axillary 

 band. 



Copulation ladder-like. Zygo- 

 spore in the connecting-tube. 

 Terrestrial and aquatic. 



86. Genus JMougeotia De Bary. 

 Cells with single, axial, chloro- 

 phyll bands. 



Copulation ladder-like. Zygo- 

 spore in the much swollen connect- 

 ing-tube. 



3. Mesocarpin^e. Sub-group 2. 

 [The arrangement we have adopted 

 for the Mesocarpinas is practically 

 the same as proposed by Wittrock, 

 but having retained the genus JMou- 

 geotia De Bary in the Zygnemiuce, 

 we have preferred to regard Stauro- 

 sp e r ni u m , Plagiosperimtm and 

 Mesocarpus as distinct genera, and 

 not as sub-genera under JMongeotia 

 (Ag.) Wittr.] 



Sy flops is of Genera. 

 Cells thin-walled, endochrome ax- 

 ial ; filaments zigzag when fruiting. 

 Gonato7ieina.i 87. 

 Copulation geniculate, spore quad- 

 rangular. Staurospermu?7i., 88. 

 Pericarpium three-celled. 



Plagiospermum^ 89. 

 Copulation ladder-like or lateral ; 

 pericarpiinii two-celled. 



JMcsocarpus^ 90. 

 Copulation geniculate; pericar- 

 pium two-celled. 



Craterosper7nn7)i., 91 



87. Genus Gonato)iema Wittrock. 

 Cells cylindric, walls thin, ends 



curved inwards, chlorophyll in an 

 axial band. 



Spores agamospores, formed by 

 tripartition without conjugation, in 

 the middle of the fruiting cells. The 

 latter bend at an obtuse angle at the 

 point of spore formation, successive 

 cells of the filament bending in op- 

 posite directions, forming a zigzag 

 line. 



[The distinctive character of this 

 plant is found in the method of 

 fruiting. The cells, unlike those of 

 the other members of this family, 

 seem not to have the power of con- 

 jugation, and the spores are formed* 

 in a perfectly neutral way, hence 



