242 Ulothricaceae and Chaetophoraceae 



Wittrock, V. B. Om Gottands och O lands Sotvattens-alger. Bih. 

 Kong. Svensk. Vet. Akad. Hand. I 1 : 1-72. pi. 1-4. 1872. 



Om Snons och Isens Flora. Nordenskiold's Studier och Forsk- 



ningar. pi. 3. 1883. 



Wood, H. C. A Contribution to the History of the Fresh-Water Algae 

 of North America. Smithsonian Contributions to Knowledge. 

 1872. 



Description of Plates 



The outlines of the drawings were made by means of a Leitz camera lucida and 

 the details filled in by careful reference to the specimens. Three combinations were 

 used, namely, Leitz ocular 3 with objective T ^ oil immerson, ocular 3 with objective 7, 

 and ocular I with objective 7, and the drawings thus made reduced one half in repro- 

 duction, so that the actual magnifications of the figures are 575, 350 and 255 diameters. 

 Most of the drawings were made from preparations made by the Flemming-chromic- 

 alum method. For convenience in identifying the material from which the drawings 

 were made, numbers of collections corresponding to those in the text, and the pages on 

 which the descriptions appear are appended. 



Plate 20 (magnification 575 : 1) 



1. Ulothrix zonata. Lower rhizoid-like portion of a filament (381), p. 148. 



2. Upper portion of the same filament. This specimen corresponds to U. attentuata 

 Kiitz., but many filaments of the same material have lower cells differing little in 

 diameter from the upper cells, showing that this is an accidental variation. 



3. A young filament with longer cells (594). 



4. Formation of zoospores, and evacuated cells ; a motile zoospore (594)- 



5. 6. Ulothrix temussima. Portions of two filaments (535) > distinguished from 

 small forms of U. zonaia chiefly by the shortness of the cells, p. 149. 



7-9. Ulothrix flacca. Apical, middle, and rhizoidal portions of the same fila- 

 ment (533), p. 155. 



Plate 21 (575 : 1) 



I, 2. Ulothrix implexa. Vegetative filaments (570 A), p. 154. 



3, 4. Ulothrix tenerrima. Two filaments showing different condition of the 

 chromatophores (645), p. 151. 



5-7. Ulothrix variabilis. Vegetative filaments (557, 574), p. I5 2 - 



8, 9. Stichococcus marinus. Contrast chromatophores with those of preceding 

 figures (570 B), p. 161. 



10. Stichococcus subtilis. Cells evacuated by zoospores (321), p. 163. 



II, 12. Vegetative filaments (427 A, 549). 



13. Filament from a drying rock, in which akinetes seem to be forming. 



14, 15. Stichococcus jlaccidus. Zoosporiferous filaments and motile zoospores 

 (618), p. 164. 



16, 17. Vegetative filaments showing varying proportions of the cells (536, 315)- 



Plate 22 (575 : 1) 



1. Stichococcus bacillaris. (637), p. 1 60. 



2, 3. Stichococcus bacillaris forma confervoidea (55°> 534)> P- I ^°- 



