16 



to distinguish the forms belonging to the Valoniacese from all 

 those in the Cladophoracese by means of this character I am not 

 able to say with certainty, but I am inclined to think it possible. 

 In the Cladophoracese we have, as is well known, a single, per- 

 forated, parietal chromatophore (sometimes with lobes also 

 in the interior), but in some forms, e. g. in Acrosiphonia, 

 the perforation is greatly developed and the chromatophore 

 therefore finely reticulated and it comes then very near to that 

 found in the Valoniacese. 



Fain. 1. Cladophoracece. 

 Chaetomorpha Kutz. 



Excluding the very characteristic species: Ch. antennina 

 and Ch. clavata (the last-named species I have however found 

 in such small quantity only, that I do not know its capability 

 of variation), the other forms of this genus are so very variable, 

 that it has often been very difficult to determine to what species 

 they belong. 



1. Chaetomorpha clavata (Ag.) Kutz. 



KuTziNG in Bot. Zeit. vol. V, 1847, p. 166. Vickers, Phycol. Barbae!., 

 1908, p. 17, pi. VII. 



Conferva clavata Agardh, Systema Algarum, 1824, p. 99. 



Only found once at the south shore of St. Croix: Lime Tree Bay. 



Geogr. Distrib. West Indies, California, Africa. 



2. Chaetomorpha auteunina (Bory) Kiitz. 

 KiJTziNG, Species Algarum, 1849, p. 379. Vickers, Phycol. Barbad., 

 1908, p. 19, PI. VIII. 



WiTTR. et NoRDST., Alg. Exsicc, No. 1439. 



The basal cell (Fig. 4 h), as already pointed out by Bornet 

 in »Algues de P. K. A. Schousboe«, p. 203, is very long, often 

 10 — 20 times as long as broad (Fig. 4 b), while the other cells 

 in the filaments are much shorter, 2 — 6 very seldom 8 times 

 their own diameter. At its base the basal cell has annular con- 

 strictions. It is fastened to the substratum by means of richly 

 and very irregularly ramified rhizoids (Fig. 5). 



The walls of the cells and especially of the basal cell are 

 very thick and consist of several layers (Fig. 5). 



The plant occurs in characteristic brush-like tufts. The 

 single filaments are very rigid. A filament cut ofl near the base 



