i8o TUFTS COLLEGE STUDIES, VOL. II, No. 3 



Order ULOTRICHALES 



Simple or branched filaments, sometimes membranes, rarely 

 in few-celled families ; cells uninucleate, chromatophore usually 

 single, band-, disk-, net-, or star-shape, generally with one 

 or more pyrenoids. Marine and fresh water. 



KEY TO THE FAMILIES OF ULOTRICHALES. 

 i. Chromatophore star-shaped ; zoospores unknown. 



3. PRASIOLACEAE. 



i. Chromatophore net-, disk- or band-shaped. 2. 



2. Cells usually red or brown by haematochrome ; frond filamentous, 



branching. 9. CHROOLEPIDACEAE. 



2. Vegetative cells true green. 3. 



3. Fronds unbranched filaments. 4. 



3. Fronds branched or membranaceous, rarely in few-celled families. 



6. 



4. Sexual reproduction by isogamous gametes, i. ULOTRICHAS^S. 



4. Sexual reproduction by oogonia and antheridia. 5. 



5. Chromatophore net-shaped. 5. OEDOGONIACEAE. 



5. Chromatophore disk- or band-shaped. 4. CYLINDROCAPSACEAE. 



6. Frond membranaceous, either flat or forming a tube. 



2. ULVACEAE. 

 6. Frond filamentous, branching, or a few-celled family ; usually 



with hairs. 7. 



7. Sexual reproduction by isogamous zoogametes. 



6. CHAETOPHORACEAE. 



7. Sexual reproduction by oogonia and antheridia. 8. 



8. Vegetative filaments prostrate. 9. 



8. Vegetative filaments erect. 5. OEDOGONIACEAE. 



9. Oospore with cellular envelope; vegetative filaments radiate or 



united to a disk. 8. COLEOCHAETACEAE. 



9. Oospore without cellular envelope; vegetative filaments irregularly 

 spreading. 7. HERPOSTEIRACEAE. 



Family i. ULOTRICHACEAE. 



Frond a normally unbranched, uniseriate filament, rarely 

 partly multiseriate, of uniuucleate cells, each of which, with the 

 exception of the basal cell, when present, is capable of produc- 

 ing spores or gametes. Chromatophore either a single, complete 

 or broken band, or a network, or one to several disks ; usually 

 with one or more pyrenoids. Asexual reproduction by bi- or 4- 

 ciliate zoospores, by akinetes, or by aplanospores ; sexual repro- 

 duction by the conjugation of biciliate zoogametes. 



