ZYGOGONIUM Kuetzing 1843, p. 280 



Filaments of short-cylindric or slightly tumid cells with lateral 

 branches, either rhizoidal or several cells in length. Chloroplasts 

 cushion- or pad-like, 2 in a cell, or appearing as 1 duplex body 

 with an interconnecting narrow band; a pyrenoid in each chloroplast; 

 at times the chloroplast showing short radiate processes similar to 

 Zygnema; nucleus in the bridge between the 2 chloroplasts; cyto- 

 plasm usually colorless but sometimes purplish, becoming brown. 

 Conjugation lateral or scalariform by protuberances from both 

 gametangia; only part of the cell contents serving as a gamete. 

 Zygospore ovate, in a sporangium which is formed between the two 

 gametangia and which splits along a median line; spore wall smooth 

 or decorated; gametangia not becoming filled with pectic substances 

 but with granular residues. Reproduction also by akinetes and 

 aplanospores (more common than zygospores). 



Zygogonium ericetorum Kuetzing 1845, p. 224 

 PL 78, Figs. 8-10 



Filaments with cells 15-24^ in diameter and %--V2-(4) times the 

 diameter in length, cylindrical or slightly constricted at the cross 

 walls; cell walls thick; chloroplasts, cytoplasm, and conjugation as 

 described for the genus; zygospore ovate or globose, 20-25/x in 

 diameter, the median spore wall smooth. 



In shallow water of Black Lake, Michigan; on damp soil and tree 

 trunks arising from water along lake margin, 



CLASS CHAROPHYCEAE 



This unique group of plants occupies an isolated position from a 

 taxonomic point of view. They have no known ancestors nor have 

 they given rise to other living plant forms according to present 

 information. They are alga-like in their reproductive habits and 

 because of their pigmentation there is ample justification for giving 

 them a place in the Chlorophyta. In many characteristics they are 

 quite unlike the green algae, however, and are so unique that in 

 some systems of classification the Charophyceae are considered to 

 be a separate division in the plant kingdom. 



The Charophyceae are all macroscopic, having rhizoidal, erect 

 stem-like branches and whorls of secondary branches, or 'leaves'. 

 They vary in height from 2 to 60 cm., growing erect or sprawling 

 in the bottom of lakes or slow-flowing streams. In many forms 

 vegetative proliferation occurs by stolons and special buds or 



[ 329 1 



