Tribonema 187 



ter form (Wittr. & Nordst. Alg. Exsic. 5/9. 1883) merely furnishes 

 a statement of the diameter, 14-16 p.. We have seen no form 

 with so great a diameter that could properly be associated with 

 Tribo?tema bombycinum. 



. Tribonema utriculosum as above characterized does indeed 

 approach T. bombycinum in respect to the diameter of the cells, 

 but the thicker cell-wall and usually larger chromatophores, as 

 well as an indefinable general appearance, sufficiently distinguish it 

 from the smaller species. By repeated observation and cultural 

 experiments, we have become convinced of the specific distinctness 

 of the two forms. 



It is a strange fact that none of these species of Tribonema, 

 elsewhere common, have been found in Vermont during more than 

 a year of collecting. 



Excluded Forms 



Conferva fontinalis Berk. Glean. Brit. Alg. pi. 14./. 1. 1833. 

 Wolle, F. W. Alg. 141.//. 120. f. 17-20. 1887. 



Microspora fontinalis DeToni, Syll. Alg. 1: 230. 1889. 

 Specimens bearing this name in the Wolle herbarium are certainly 

 a Rhizoclonium, and probably the same is true of Berkeley's type. 

 Berkeley supposed he was illustrating Conferva fontinalis Linn., 

 but it is very doubtful if such was the case. 



Conferva bombycina elongata Tild. Am. Alg. 21 is a Rhizo- 

 clonium similar to Wolle' s C. fontinalis. 



Conferva sesquipedalis Tild. Am. Alg. 271. is Zygnema sp. 



Conferva Sandwicensis Tild. Am. Alg. 4.62. Hawaii, 1900, is 

 RJiizocloninm sp. showing the pyrenoids very clearly and giving a 

 strong test for starch. All these examples of incorrect generic 

 determination show how little the true Conferva {Tribonema) has 

 been understood in this country. 



See also doubtful forms of Microspora. 



Genera removed from the Ulothricaceae 



Schizogonium Kutz. (Phyc. Gen. 245. 1843), including, accord- 

 ing to the revision of Gay ('91), Ulotlirix-like filaments which have 

 stellate chromatophores and exhibit a strong tendency to longi- 

 tudinal cell-division, and even to form an expanded thallus, is re- 



