22 COLLINS AND HERVEY. 



of the opinion that there is no justification for keeping color forms 

 distinct taxonomically. Both colors occur in nature, both in dried 

 material; plants originally aeruginous may change to red, plants 

 originally red fade to pale green. We have no suggestion to make as 

 to the causes determining these changes, except the general principle 

 in regard to filamentous Nostocaceae, that red forms generally occur 

 where the plant is always under water, not left exposed at low tide. 



4. L. SEMiPLENA J. G. Agardh ex Gomont, 1893, p. 158, PI. Ill, 

 figs. 7-11. Not uncommon among other small algae; rarely pure. 



5. Lyngbya lutea Gomont, 1893, p. 161, PI. Ill, figs. 12 & 13. 

 Among various small algae, not found pure; bright red form on 

 C odium, Harris Bay, Dec, Hervey. 



*6. L. Lagerheimii Gomont, 1893, p. 167, PI. IV, figs. 6-7. On 

 decaying Sargassum, near Shelly Bay, April, Collins. 



Symploca Kiitzing. 



1. Cells 1-2 diam. long, aeruginous. 1. S. muscorum. 



1. Cells much shorter than their diam., violet. 2. S. violacea. 



*1. S. MUSCORUM Gomont, 1893, p. 130, PL II, fig. 9. On rock by 

 roadside, Aug., Collins. 



2. S. VIOLACEA Hauck ex Forti, 1907, p. 311 ; Hauck, 1885, p. 507, 

 fig. 224. On ground near margin of pool in woods by Walsingham, 

 April, Collins. This appears to have been overlooked by Gomont in 

 his monograph either as an accepted species or among "species in- 

 quirendae" or "species excludendae." Hauck's record is included 

 by Forti in the Sylloge, and by the international rules, which fix 

 Gomont's monograph as the point of departure for homeocysted 

 filamentous Nostochineae, 1907 is the date of publication. The 

 Bermuda plant agrees with Hauck's description and figure; the violet 

 color and short cells distinguish it from all other marine species. 



Plectonema Thuret. 



*P. NosTOCORUM Bornet ex Gomont, 1893, p. 122, PI. I, fig. 11. 

 Common in gelatinous masses of algae of various kinds. 



PoRPHYROSiPHON Kiitzing. 



*P. NoTARisii Kiitzing ex Gomont, 1893, p. 69, PI. XII, figs. 1-2. 

 On Juniperus henmuUana, Aug., Collins. 



